blazer rear seat help

[briank]

I have a 70 blazer that never had a rear seat. Plan on putting one in but the under floor bracing I have to put in is out of a 72 blazer. The seat is out of a 69 blazer that has four rear mounts but the center two dont line up with the two on the bracing. How many different braces did they use? I also have rear seats with just the two rear mounts as well, both out of 72 blazers, anybody else run into this problem? Id lile to use the 69 seat in it because of the interior pattern.