So I was searching the internet about random fiero parts and stub led across this website called
www.cheetahonline.com they are a custom engineering and manufacturing company. They make the 12" Corvette brake adapter brackets. And they also make the concentric rings to go with them. I saw this and inquired about the company. They have an address and their phone number works. They also sell parts for Porsches and other vehicles. The only reason why I posted this is because I couldn't find if anyone else had found this site. They sell all for brackets for the upgrade for $100 plus shipping. I have the brackets for this swap but had them custom made and they cost me about $300. So $100 plus shipping would be an awesome deal for most people.
