Hi Jim, is your power brake booster a single or a dual? I am sure I will be in the same boat as you since I am running a big hyd. roller cam which only puts out 10" of vacuum. So I will be running a vacuum canister hoping this will solve issue with running Wilwood disc brakes at all 4 corners. With a BBC in a 30 roadster I certainly want to be able to stop it. There is a way to run dual master cylinders that are manual (no vacuum needed) with a slave bar attachment if worse comes to worse.