RPO codes for a 9c1 car

I have a 1978 Impala 2 door but has a 8.5 rear end and the vin come to having a corvette 350 witch I believe is part of the 9c1 package but I was confused when I went to replace the rotor and the it measures 11inches but under auto zones system 11inch rotor measure 12inches and the rotor for my car was under the 9 inch rotor. Does anyone have the rpo codes for a 9c1 car.

RPO/SPID codes are the same for all Chevys.
You're not deciphering the VIN correctly, NO B-body ever came with a "Corvette" engine.
Rear disc brakes were not available on Impalas or Caprices even as an option in 1978. If you have rear disc brakes, either the rear has been replaced with a newer one, most likely out of a bubble 9c1, or they've been swapped over from a late 70s Buick Rivera or Caddy Seville.
Most likely the rear was swapped.

A bit of advice.... don't listen to anything the knuckleheads at Auto Zone say. You MUST go there knowing what you want and don't rely on them for anything if you want the correct parts. It's been my experience that they are absolutely clueless when it comes to older cars. LOL, newer cars too! They were probably looking up the front rotors, not the rear.

There's threads on here with all the info you'll need. The search box is your friend.

Ok after reading my post I apologize on my not being clear on what rotor I was talking about the car came with an 8.5 rear end a 350 don't know why I put corvette in front of it. The front rotors not the rear are 11inch. My question is did most 2 doors come with the 11 inch rotors on the front or the smaller size. But also did most 2 doors come with the 8.5 rear end? Thank for clearing me up. Phil Fenwick

The 8.5 rear doesnt have anything to do with the 2 or 4 door, only special options, like f41 suspension or towing package, even having a 350 didnt mean you got an 8.5. But to be honest, they should have never came with anything other than an 8.5. All b bodies from 77-90 had 11" front rotors being only the 9c1s got the 12", and only the 91-96's got the 12" front rotors from the factory. IIRC you can bolt the later 12" rotors on the earlier b bodies with 11" rotors, because they use the same caliper, and the rotor actually measures 11.86"

Ok thank you that helps out a lot.

Idk about anyone else, but Id love those RPO codes. Specifically, for a 96 9c1. I have almost came to the conclusion that NO one has them anymore, and its just a matter of hunting.

Thank you! Now to do a control f search at work later and see what kinda 9c1 stuff i can come up with I guess. Btw, I have pics of my Beast, I guess I just cant post any links for a few more days since im a newb here.