Re: 67 J-2000
spicer gear box?? u mean the xcase? and if so, did u swap in the 300 case?
i c no probs to swapping the GM stuff cept for these:
the front springs on ur j2k are bolted outside of the frame. GMs are not. ud have to weld in some nu spring mounts right beneath the frame rails, not hard to do, just takes a good welder.
the other concern is the distance between the spring pads on the j2k's frame and on the rear axle of the GM. if they aint da same, the mounts on the GM axle wood have to be moved to accomodate the Jeep frame.
next u wood want GM axles from pre 77 4x4s using the genuine d44 axles. the GM 10 bolts (on 77 and up) have less stamina than the axles u have now.
if this is too much, u can always use genuine jeep axles from 74-79 j10s and j20s. cept for moving the spring mounts under the frame up frot on ur 67, theyd be a bolt in.