Help needed w/1969 body on 1972 chassis

[CBx4]

My son purchased a Chevy truck that was being restored and has a 1969 body on a 1972 chassis. The truck has been lifted and he wants to add 4 wheel drive. When he purchased the truck he was told it could be done that all he needed was the linkage. Can this be done and how hard/expensive would this be? Thanks!

[JJmakeitgo]

If the '72 frame was already a 4x4 it woud be easy. just need front drive shaft and transfercase, if not you would need to take the front suspension out and replace with leaf springs and a diff. The frames were alittle different between the 2wd and 4wd there would be some customizing needed