I heard you need 16" with the F-body brake (12") and 17" with the C5 brake. The hub assembly would allow you to run the Brakes off of an S-10, which I have seen squeezed into a 15" wheel.
I should have pricing in the morning on something 5/16" in aluminum from my machinist.
I hope I'm not stepping on anyone else's toes.
I know this is my first post, but I've been browsing for a Turbo Buick and I'm an admin over on Maliburacing.