Thumper RA Tech sells pinion depth checkers that are less than 300 bucks, they sit between on the pinion head and you measure against the carrier bores a certain way to check depth, using the depth indicator on a pair of veneer calipers.

I just bought one to use on my 8 3/4. I'm sure it won't be perfect, but will give you a good start, then adjust based on the pattern. People with the high dollar mics say they often need to adjust based on the pattern anyway, as the depth from the manufacturer isn't quite perfect. You can buy the tool on summit and they're application specific. Reviews on them have been pretty good.

http://www.summitracing.com/parts/rat-10007/overview/