No the suspension will not swap. The GMT 400 chassis ('88-98) has the control arm mounts wlded to the frame rather than bolted. Also, the wheel base is longer by avout 3". Even the '73-'87 chassis has too long of a wheelbase for use under a '60-'66 body. I'm with TMTC, do the bolt in front suspension/brake swap, keep the coils in the back (better ride), then get an engine from the salvage yard form the later truck. I can understand getting a complete doner, but you'll be ahead doing the swap separately than trying to find a 1 yaer only truck as a doner.
PS- you only really need the spindles for the disk brake conversion, and ball joints from the later truck.
