[badpeanut]

While not really what you are looking for, thought I'd share:

• '67-'72 leaf spring truck 12-bolts (4x4 and 4x2) have non-staggered shocks.
• '67-'72 4x4 trucks have 2" wide spring perches 41" centerline to centerline and bump stop provisions on frame.
• '67-'72 4x2 trucks have 2" wide spring perches 43" centerline to centerline and bump stop provisions on rearend.
• According to the Hollander interchange the '70-'72 axles on GM 12-bolts are 31-11/32" long and the '67-'70 are 30-1/4" ('70 is a split year).
• '73-up 12-bolts (4x4 and 4x2) have spring perches 43" centerline to centerline, bump stops on frame, staggered shocks, and 2.5" wide spring perches.