Ford and Chevy part is the same size?

[Tony Smith]

By "Body Part", do you mean the cab panels, or the rear bodywork?

Ford and Chev cabs share very little in common in the way of sheetmetal panels, although some parts will interchange, eg Doors, seats, cab roofs.

The rear body work is a different story, with both chassis having the same dimensions, so all GS bodies, "House" bodies and even Gun Tractor bodies will interchange