8.75 for my A-body

Okay, I have found several piece of crap vehicles that have 8.75 rears in them and am considering buying one. Most are old vans. I understand the spring perches need to move and the tubes will have to be cut. Where do I find specs, and what do I have to do about the axles? I hate to sound ignorant, but this is my first Mopar and I have to learn as I go.