The Shop Manual and Vette Forum DIY's are fairly formidable ... especially compared to the VW's I use to do.
The nominal diameter of the p-brake drum, which is part of the rotor, is 7.50." Verify this dimension by measuring at several points. On my car, both drums were slightly smaller. The left side drum diameter was between 7.471" and 7.477." I used 7.475," the average of five measurements, as the diameter. This dimension must be .028" to .036" larger than the lined shoe diameter to provide the correct .014" to .018" drum-to-lining clearance all the way around.
To make this clearance .016," I set and locked the caliper at 7.443" (7.475" minus .032"). You may want to use a few thousands less--if I did the job again, I would try for a total clearance of about .024." Tap the shoe here and there until it looks centered on the wheel hub. Then, using the locked caliper as a "go-no go" gauge, hold it horizontally right over the centerline of the threaded spindle.
