The title says it all. Can anyone answer?
Darned interesting question. And I happen to have one of each here. I haven't done a photobash yet, but I did notice that the drivers are almost the same size, and almost the same spacing. The cylinders on the On30 are much wider than the HO, because the outside frame means that the driving rods are further out from the center, so you would most likely have to use the HO cylinders, and that is where any trouble would most likely arise.
If I have time, I'll take photos of each, and see how this would look. It's a simple way to see if an idea is worth pursuing. The second step is to disassemble both locos, and do a test fit. That's a major project. I do recall seeing the HO 2-8-0 mechanism used under a Mogul body, and it looked interesting.
I'm thinking, not so much, unless you shorten the On30 boiler, or add a trailing truck to make a 2-8-0. The HO mechanism is just too short. Turning a Mogul into a 2-8-0 would be a safer bet, I think.
(http://lh5.ggpht.com/Gresham.Media/SIuMZrq_YZI/AAAAAAAAAKk/4p5prSMnqRc/280-Test.jpg)
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