I had a 68 assembly, It had an additional brace welded to the pedal box, otherwise it looked identical.When i tried to combine the best of both 68-69 I found that there were clearance problems between the pedals where they fit in the brace.Also I think there was a slight difference in overall length that may have to do with the dash board to firewall difference.Dont know about the 70-81 but I suspect the angle and length are not the same. Goodluck- MIK