['ol Pinion head]

C-clip axle 8.2 Chevy-8.5-12 bolt A-F-X backing plates interchange amongst each other. Only exclusion to that rule would be the rear backing plates on an extremely rare 12 bolt rear out of a '65 L16 Chevelle.

The factory use of spotwelded on flange on c-clip axle backing plates used with 9.5" diam drums came to an end at the end of the '74 models. The extra long parking brake cables on early 2nd Gen F-body backing plates disappeared at the same time.


Slightly larger diamer center hole-- i.e., bolt-in axle 9.5" drum backing plates interchange amongst theirselves. There are several different styles, but as long as the rear's axle carried a sealed bearing rw507 axle bearing or a A9 tapered axle bearing, the center holes will be the same size, & backing plates will interchange.

Oddball 9.5" drum backing plates...
Larger diam axle bearings like those used on '67-68 31 spline axle type "O" rears, & at least two styles of Buick & Olds A-body station wagon rears, all these required specific style backing plates, & on one occasion wider rear brake shoes.

Following is for those interested, but ESP, Serious Restorers.
The factory use of c-clip axle spotwelded on flange type backing plates used with 9.5" diam drums came to an end at end of the '74 GM models. The use of extra long style parking brake cables on F-body backing plates also disappeared at the same time.

Last, the 9.5" style backing plates used on McKinnon built 12 bolt c-clip axle rears (used in certain Buick, Olds, & Pontiac A-body applications) did not have the spotwelded on flange. On several occasions, have spotted incorrect detailed supposedly correct 12 bolts under '70-72 455 GTO's. McKinnon built 12 bolts of this variety also used their own style 12 bolt axles with the center pilot being slightly larger diam than the much more common axle used in typical 12 bolt c-clip rears (Chevrolet uses). While original Chevy usage A-F-X 12 bolts continued to use "smoothy" style drums, the McKinnon built 12 bolts like used in '70-72 455 Pontiac A-body's & GP's used the finned rear brake drum. This finned style brake drum was installed at the McKinnon axle plant & will have a stenciled/painted on two letter rear end ID code towards the center of the drivers side rear brake drum. No two letter code color bands were installed on McKinnon 12 bolt axle tubes like we're installed on early Pontiac 8.2 10 bolt rears.