[Will]

The late '70s to late '80s or early '90s (not sure on the exact years unfortunately) B-body spindles are direct replacements for the '70 - '81 F-body spindles. Therefore, they can also be used in the A-bodies as mentioned above with the special ball joints and modified upper control arms.

Many of the B-bodies were equipped with 12" rotors from the factory, usually cars with towing packages or heavy duty suspension or brake options. I have two sets of these spindles, one set came from a '78 GP cop car and the other came off an '86 Caprice wagon.

The problem with these 12" spindles is finding a reasonably priced rotor. The rotors that come on them originally have a 5x5 bolt pattern and I'm not so sure redrilling the rotors for the correct pattern will work as the area of the rotor where the studs go through it is reinforced around the existing stud holes and relieved elsewhwere.

This leaves your best choice for a brake rotor as the late '80s Camaro/Firebird 1LE rotors, which are about $100 each new and are designed for a metric wheel stud, though you can find SAE studs that will fit. They take the same wheelbearings and will bolt right up to the B-body spindles.

As to the need for larger brake rotors, it has more to do with repeatability under extreme conditions than any lack in the stock system for normal use. For a normal street-driver, the F-body or original A-body sized rotors are fine. If you intend to autocross or roadrace then you will need the biggest brakes you can get, and if you're on a budget then the 12" rotors are the way to go.