David,
I think you are correct about the cabs being the same. The differences are in wheel size and springs etc.
Here are links to colourful and easy to read specifications that were provided some time ago by a Mr. G W-B
:
CMP Chev specifications:
http://www.mapleleafup.org/vehicles/.../chevspec.html
CMP Ford specifications:
http://www.mapleleafup.org/vehicles/.../fordspec.html
HTH,
Brian
