Lowering a C30 motorhome.

[chopttop]

Have had a C30 w/motorhome on frame for 4 years now, 350/400. Took it to Sturgis first year, ran well but stopping was a b'itch, would like to use it more. Been reading on swapping crossmembers from newer truck to get disks. Found a donor truck, '80 C30, w/mid 80's , low millage, 454. will remove engine, front suspension, 6 newer michelin tires, newly reduilt 4 speed w/granny gear? and what ever I need and scrap the rest, paid $700.
I have a '71 w/dropped spindles/springs and shocks front and dropped leafs in rear. I would like to do the same to the '70 and should not have a problem w/the '80 suspension, what is the best thing for the rear w/the springs?
Would love to dropmember and bag it, would be the shts to lay frame w/a big old classic motorhome But have to many classics needing different mods.