The way I'd go would be to buy a wrecked (rolled) early to mid 70's GM 4X4 and use both axles and the brake system complete. Then sell everything else that's useable from the swap,including your old axles and parts, on ebay to recoup your purchase,and order the rear disc brake conversion kit.It's also available from JC Whitney. My 2 cents worth...
Speed


1954 GMC 350
1957 GMC 1/2 ton
1962 Chevy C-30
1952 Chevy 6400 dump bed project truck
'98 Harley FLSTC
'66 Pontiac Catalina
'76 Chevy 1 ton Duallie
'84 Bronco II
'78 Dodge W-200
'81 Toyota 4X4 truck