Stephen , UP's version of the FM Erie Built (rd# 652-57) series match Atlas's pretty much dead nuts, at least with regard to trucks or wind shield. When you say "chopped roof" are you referring to early model rectangular windshield aka the "B-17" version ? UP did buy the Erie Built demonstrators(650A-B,651 which I would guess had that windshield and the custom factory trucks) but it would not be representative for the rest of that model on their roster.
Bob, are you familiar with LWS's Erie Built? I see Mr. L listed them for about six years.
Pete