I asked this question in the excursion section, but have had no responses:
How hard to put a cab off a gas motor truck onto a 6.0 motor truck (03)? Would this be straightforward with the in the dash stuff? Any differences in other years or other pitfalls?

 

I would expect a few differences but nothing that would stop it from mounting up the same. I'm guessing the firewall wiring or other things could be in the same spot but might be configured differently.

So if you had a bare gasser cab it's going to fit. You may need to punch out different spots for the wiring and such.