Discovered something unexpected about my car. I had an overheating front left brake, and the cause was basically that the car was stopping intermittently on only that brake. My mechanic set out to bleed and replace the lines. My front brakes - pads, calipers, and rotors - were replaced in June, but the rears were original. So I told him to check them out, replace the pads, and do whatever else was necessary to get the rear brakes back in good condition.

I assumed that my GTA had factory discs all around, since that was standard on those cars.

Turns out that my rear brakes apparently were drum from the factory, but where converted by the prior owner. This really surprised me, as the car only had one owner and appeared to be 100% stock except for tires when I bought in February of 2018.

They had a hard time finding pads that fit exactly right because of the non-OEM rear brakes. They ordered a number of different sets of pad and ended up trying a set of pads for an '85 Chevy S-10 back there. The fit wasn't perfect, but it's very close. The car is now braking better than it has at any time since I bought it. Feels like new. The original plan was to install new calipers and rotors in the rear, but with difficulty they had finding matching parts and with the car being low mileage, they were able to resurface the rotors and clean up all the hardware pretty well.

I did some research and saw that there were some GTA optioned down to rear drums, but this was typically on 5.0 cars with T-Tops. not with 5.7 motors. There's an RPO code (J42) for this. I've also heard various stories about cars, not always f-bodies, where the factory simply runs out of parts and makes substitutions. I don't know what the case was with my car, but I wonder if it was something like that. The car was so stock that it would have been really surprising to me if the former owner actually had a disc conversion kit installed.