Yes, you are correct. Welded shut the Seville caliper mounting plate mounting holes and drilled new holes to match the '71 Riv's axle flanges.
Montaz all the info you stated is correct minus one thing.. the pontiac rear is not a bolt in axle.. it is 31 spline C-clip. Side spider gears are the same and interchangeable though with the olds 9 3/8
ALL 1971- 1976 are BOLT in axles for FULL size BOP - Chevy may have had a version or the rear is a newer 1977-1985 31 spline c-clip rear. 10 cover 12 ring. A-body 73-77 also had a 31 spline 10 bolt cover 12 bolt ring pontiac rear that had the smaller 1.625 pinion shaft...Monte Carlo, regal, cutlass etc. You have to remember the age of your cars and the likely hood original drive line parts are still in it from 40 years is NOT likely. Jim
