I concur that the model, if done, should follow the South Park prototype.  Doing a version without the pilot wheel and a different stack would serve well enough for the Peach Bottom fans out there.  The Revere Beach locos were a whole other story.  The current Sandy River Forneys are a bit closer, though the driver sizes are considerably different.

The more I think about it, the more I like the idea of a Mason Bogie.  I would think Bachmann could make as either an 0-6-6T (Peach Bottom and others) and as a 2-6-6T (South Park).  I might get one just because they're neat, though I have no use for one on my pike.

To answer more directly the original question--On30 uses the same wheel and track standards as HO.  Yes, you can use code 70, even code 55 (though that is really too light for O scale track, at about 20 lb. rail equivalent). 

The 2-8-4's on the C&O did not have "flying pumps", but the 4-8-2's did.  Due to tight clearances in the tunnels along the New River, the C&O mounted the two cross-compound air pumps on the smokebox front instead of alongside the boiler.  They did this also on some 4-6-2's.  Bachmann makes the 4-8-2 in C&O as part of the "George Washington" passenger train set.  See a pic in the Bachmann catalog.

I think I should qualify things a bit--there are in fact track and wheel standards for On30--they are the same as for HO.  For clearances in general, the On3 standards should be considered.  However, as with most narrow gauge modeling, you have some discretion depending on your particular prototype.  Same goes with coupler size and height.  Bachmann has used the typcial HO standard, using standard HO couplers, and that's OK for On30.  If you are using some of the On30 equipment for On3, then you have a bit of work to do to raise the couplers to On3 "standard" height.  Recent Bachmann releases have two-level pockets for this purpose, but they only accommodate the HO coupler.  If you use the Kadee 803's, then you will likely need to do some cutting and fitting. 

Arttista makes a very good line of 1/48 figures, most pre-painted.  I heartily second the motion for some true 1/48 vehicles.  Aside from some very hard to find Revell and Monogram kits from the '60's, and a few case metal old-time vehicle kits, there is virtually nothing out there.  I've got a pile of the 1/43 vehicles because that's what's been available for my early '50's era pike.  Sure would like to see a Ford Model A, a '49 Ford, a 55 Chevy, a nice "woody", an early '50's pick-up (make not important).  You get the idea.  Let's not see "rare" or "high-end" vehicles--imports, Caddilacs, Edsels, and other stuff that the large bulk of working folk would not be driving.  I happen to think that Bachmann could open up a whole new market by doing a line of scale vintage vehicles that just happen to be compatible with their On30 line!  (Hint, hint!!)

FWIW, I have not yet seen ANY loco with factory sound that had the chuff rate synced anywhere close to the driver revolutions.  Many seem to come close to 2 per rev, but not 4.  All DCC locos have the chuff generated electronically, increasing as the voltage increases.  They are not directly synced to the drivers.  While you may not get the chuffs to "fire" exactly at each 90 degree point, if you get them close to 4 per rev you'll be fine.  When you do try to set the sync, do it at low speed, where the effect is much more noticable to the eye.  At moderate to high speeds the chuffs begin blending together, and you can't really tell by eye whether there are actually 4 beat per rev or not.

I think you're essentially right, Harold.  The coupler height for the On30 equipment is set based on the use of HO couplers, and hence the height required for them.  It is serendipidous that they might match a prototype 30" gauge line.  As you might have noted, some of the new stuff is coming in with double coupler boxes to accommodate the On3 couplers if one chooses to go that way.

Re:  Early EBT--FWIW, MMI is supposed to release a model of a C-19 this summer in On3 and On30.  List price is about $450.  A bit of history of EBT 7:  It was built as a copy of the D&RG engines, but came with a capped stack instead of a diamond stack.  It ran pretty much stock into the 1900's.  In 1907 she got caught in a shop fire, which destroyed the cab and did other damage.  The engine was rebuilt with a new steel cab of the same design as the Mikes have today.  She was sold to the OR&W in 1913, and survived there till the end in 1936.  At some point, the main rod was moved from the second to the third axle, and she acquired a new tender (maybe on the OR&W).  So far as we know, the engine kept the Eames vacuum brake system throughout her life.  

The Bachmann Mogul is a model of a DSP&P Mogul (later C&S).  The W&W locos were a bit newer and somewhat distinct in their appearance.  I'll give credit to Bachmann for doing their model in PRR lettering, but it really is not the same loco.  I've actually seen the W&W loco in operation.  It is located at the Greene County fairgrounds near Waynesburg.  They had it runable back in the mid-'80's, though only on about 100 yards of track.  The people who maintained it back then left or passed away, and the engine sat for about 15 years inside the shed, where she lost some parts along the way.  They have it painted W&W on one side, and PRR on the other.

  Lee:  Great EBT shot.  Perfect light and everything.  On the broader subject, try and find yourself a copy of Hilton's book "American Narrow Gauge".  It covers virtually every common-carrier narrow gauge in the country.  It does not, however, cover items like logging roads or industrial plant lines that were captive and did not (normally) interchange.  Pennsylvania along had a long list of N.G. lines.  Longest-lived were the EBT (still running) and the Waynesburg and Washington (quit as a narrow guage line in 1936, though the PRR actually wide-gauged it and it hung around intact until about the late '50's).  Side note--it would be neat if someone (hello, Bachmann) would do the W&W Cooke Moguls.  The Pittsburg and Western ran out of the oil feilds around Bradford down to the Steel City.  The B&O took it over in the early 1900's but ran it 3' for a few years before wide-gauging it.  The Knox & Kane tourist line uses a part of this line.  It also interchanged with the Tionesta Valley RR, which ran south out of Sheffield.  It was primarily a logging line, but had some decent milage.  The G gauge outside-frame Heisler is modeled on one of their engines.  There were a lot of lines that were gone early-either absorbed into the big roads or just abandoned.  The famous Ma & Pa was originally narrow guage, and the predecessor Peach Bottom, Eastern Division, became the Lancaster, Oxford & Southern which lasted until the early 1920's.

There were also the Tuscarora Valley and the Newport and Sherman's Valley lines.  Again, both lasted into the 1920's. 

The south end of the Ma & Pa went through several road name changes, including the Maryland Central RR and the Baltimore and Lehigh.  The latter had a 2-8-0 that was a copy of the D&RG C-16 class locos.

In Dixie, you had the Surrey, Sussex & Southampton, a mostly-logging road but with some line-haul.  One of their 2-6-2's is at the Pine Creek RR in New Jersey.  The Southern had a narrow gauge line they acquired, which was in the same general tidewater area. 

The West Virginia Central served coal and lumber interests out in deepest West Virginia.  Some of that line was taken over by the B&O, some by the Western Maryland.

The more well-known lines--Lawndale and ET&WNC got great press from Beebe and Clegg, mostly because they were still around in the 1940's.

Go here for a pic of a fairly typical RS-3:  http://www.readingrailroad.org/roster/roster_loco_485.html

Uh, the Minnesota Commercial loco is a switcher.  Not sure what model designation was given by MLW.  The RS units were road switchers, with a short hood behind the cab.  The RS-1's had somewhat boxy hoods, whereas the later models were rounder on the hood corners.  They came in both 8-wheel and 12-wheel versions.

I guess my thought is that this is such a unique, one-of loco that the Bachmann folks would not be inclined.  They are generally looking for prototypes that have broad appeal and/or can fit into several different road types--See, USRA 2-10-2; Russian Decapod; Richmond 4-4-0.  The model has been done in brass a number of times. 

They were probably referring to one of the early Alco road switchers--RS-1, RS-2, RS-3, etc.  They were fairly common in the '50's and '60's, but are rare today, and most that are left are in museums or on tourist lines.