Well, the most coveted bolt-in combo swap is the Dana 60 front, 14 Bolt full floating (14bff) rear. These are direct bolt in.
Keep in mind, the 14bff needs to be out of a 3/4 ton truck, otherwise the spring perches need to be moved. The axles (well, hubs) for a single reae wheel and dual rear wheel are different. The hubs might need to be changed, unless you are running wheels with a LOT of backspacing. Axles from vans are different lengths too. Driveshaft modifcation might be necissary too.
It is a fairly easy and straitforward swap, as long as you have all the correct parts and basic hond tools and knowledge.
Do some searching around here, as many of us have done this exact swap.