Why.   The walthers has a real can motor in their loco. I think you can put in a atlas or nwsl motor alot easilier  because of the 2mm diameter shafts will fit the existing walthers flywheel.  I compared a Atlas motor that I happen to have from their trainmaster and the body length is very close to the walthers but the body height is smaller so you may have to put some shim or clauking to keep the atlas motor from spinning within the body mounts.  NWSL lists their motor's body sizes on their web site so you can get a very close match.  hope this helps

I would like to see sd70ace or sd70m-2 and a GE es44ac

There is a big difference between the wallmart and the boxed versions. I own both. The wallmart has less moving parts ie. the wallmart bull dozer has molded on tracks and the boxed version has rubber tracks that can move. There are also some other detail and paint differences. In this case you get what you pay for. Dont get me wrong, IMHO, for HO Scale at a quarter of the retail price, the walmart stuff is more than adequate for a model railroad. If you have a construction equipment fetish or collect diecast you may want the boxed stuff.