I can't remember for sure, but I think the width flange to flange was the same, but in 68 they staggered the shocks, so the mounts will be different. Also, all 67's were monoleaf with smaller brackets, but many 68's were multi-leaf. Hope this helps. Steve Laabs
If the 68 is single leaf it will fit right in. Just use your present lower spring plates with the shock mounts on them. 67's didn't have a U bolt they used four studs. Punch out one pair of studs each side and install your single U bolt on each side. you may have to enlarge the holes.
If your 68 is multi leaf there is more to do.
The older I get, the faster I was!