Cummins, Allison combo
 

Just bought a fixer upper 04 GMC 2500 and the head gaskets are starting to go on it. Just wondering what all I'd have to do for it to be able to drop a 12 or 24 valve Cummins in it. The Cummins is about 300lbs more so I'm imagining getting 1 ton axles would probably be beneficial and just wondering what else I should do. (I know the electronics are a whole other bag of hammers but I can do that part) I'm still kind of new to working on cars so Lehman's terms would be appreciated.

Thanks for any input!