I recall hearing that the 3 window cabs (70 Class, C-19's had them when delivered) were awkward to run because the controls were far apart. In the big cabs on engines like 432 (C-15 375) the engineer had to get up and walk forward to adjust the Johnson bar then walk back to the seat to adjust the throttle. So that may well be the reasoning on the 45's. As for the front end, diamond stack, short smokebox, straight stack long smokebox. Just depended on where the spark arrestors were. There was lots of experimentation in different front ends during the era.