More weird swap questions.....

[qksilver]

Bought a 68 c-30 wrecker 2 months ago for 4 bills. You can imagine what condition it's in for that price.
I have all the sheet metal to get it back to good shape but have questions about mechanical stuff.
The truck orginally came with a 6 so the rear has really deep gears, thought about a 5 speed swap but don't have the money.
Found a complete C-40 truck cheap with a good running 350, 4 speed and a 2 speed rear. Frame and body are wasted but good running gear.
Question is can I install the C-40 rear under my C-30. It has the dually option so the wheels stick out past the body and the wrecker bed has fenders.
So width sin't a problem, I can trim the fenders if I need but are the spring perch widths the same the same on the rears and is it possible to fit 16 on the C-40 rear or can I use the C-40 wheels on my C-30.

I am not able to go to the C-40 and measure stuff for many medical reasons and if I don't buy the truck it is going to scrap.
Any help would be apreciated
Thanks,
Steve