Originally posted by Turbo6inKY
Poke around on Wilwood's website. You can download a PDF with the installation instructions for their front-end kits, including the kit for the G-Body.
In that PDF file is a scale drawing with measurements of their bracket, which is a big piece of plate steel. Their kit uses a stock-diameter rotor, but you can get the needed spindle modifications off the diagram, as well as how to drill the plate to fit on the spindle.
You'll have to figure out where to position the caliper mounting holes on your own.