another question on disc brakes

[gmc67swb]

Swapping over to disc on the front,The question i have is,on my 67 gmc truck can i use the upper and lower control arms on the truck are do they need to be replaced? The reason i ask is all ball joints and bushing are only 2 years old. I Have a 72 front disc set up as the replacement. I figured if i could swap spindals for now then build up the other arms for the future. Any help on this is appreciated.....thanks