I should add...
Joe F did my Allegheny and he does fantastic work!
Yes diesels with removable bottoms on the trucks are the simplest to do. I did so many that I started getting lazy and looking for RTR. Whenever I can't find a particular model in 2 rail, I convert a 3 rail one over. I just did three last month that had been sitting in line for almost a year. Of course, right afterwards, the same models came up for sale in two rail.