The subject has been beaten, but I'm not sure we've heard the end of it yet! There was a long string (I hope still in this forum's archive) on "PA-1 Traction Motor Question". Note that at least some early PA-1 were apparently built with the big 746 motor, and that Doykle McCormack hopes to operate his PA-1 on Erie-built trucks with (I would assume) 752 motors(*): so even if the motors are not the same size, it is apparently possible to adapt the trucks to use either. (It may involve modifications to the bolster: I don't know.) ... Thanks for the confirmation that GSC did castings for all three truck variants!
(*) For that matter, Canadian National's C16-5 had hind trucks which, at least visually, seem to be like those on the Erie-builts, but with 752 motors.
From a modeling point of view, the two inches difference in wheelbase between a Dl-109's trucks and the others is hardly going to be visible in HO scale. The difference in shape of the truck frame between the post-WW II Alco and FM units is visible (look up the relevant railroad's locomotives on George Elwood's "Fallen Flags" rail picture site
but subtle: only the most fanatical rivet-counters will notice!