['ol Pinion head]

Re Jon: can't handle all the parsed links/quotes. Very hard to read & follow.

1) yes, '71 Pontiac A-body's with 3.90 HD STT were seldom ordered, dealers & salesmen seemed to know the wide ratio Muncie & 3.55's provided the best performance with the stock 71 400 4bbl engine.

2) No such thing as a "BOP" 10 bolt, have gone into depth on this many many times. The style of rear you are referencing is known as the PONTIAC late style 8.2 rear, it was introduced in later production '69 Firebirds, & continued on under '70-72 Pontiac A-body's & GP's. Olds & Buick did not use it.

3) Was referencing Pontiac gear ratio availability in '71 & 72 A-body's.

4) '72 Pontiac A-body's continued to use the PONTIAC 8.2 late style 10 bolt style rear, no early 8.5 A-body rears were used in Pontiacs. The Late Pontiac 8.2 is noted by 7/16" diam LH thread ring bolts on the ring gear, & tapered bearing axles. The 12 bolts used in '72 A & G body's when ordered with 455 engines continued to be McKinnon plant 12 bolts, McKinnon plant specific cast center housing, 3R pinion flange, specific c-clip axles, smooth style backing plates like used on Pontiac 8.2 rears, not the spotwelded flange Chevy style backing plates. This version of 12 bolt rear was not same as avail under a Chevelle, where the 3.73 axle ratio was optionally avail.

5) would have to dig out that particular roadtest, try & see if can note if the car was preproduction model. Pontiac Engr could have easily specced 3.90 gears, there is a factory Chevy part number for 3.90 12 bolt gear set. Have noted before there were at least two '70 RA4 T/A's invoiced out to Pont Fact Engr, eventually being shipped south & sold as used cars in late Feb '71, one could have been the magazine test car.

6) the 3.90 ratio was first optionally avail in a GM A-body in an early PONTIAC 8.2 rear in a '64 GTO. Was not avail in an early Buick 8.2 rear which came in a late season '64 442. Have ran across a few early Pontiac 8.2 STT rears with optional 3.90's. More common to run across 3.90's w a 3spd in an earlier production GTO's, def a price leader type build.