Say Moby, what are you putting this into?
If you are sticking to the high vacuum thinking the booster needs 18", you may be cheating yourself from some extra power.
See, the big-cam engine may idle with a low vacuum, but you don't drive the car at idle! You can pick a cam with only a little lower idle vacuum, but pops right up as soon as the engine hits say 1800rpm,the typical stall speed. So by the time you are 1 car length out of the gate, the booster is fully charged. And if the check valve is working right, and the booster is working right, it will store plenty of vacuum, to provide plenty of assist.
So, depending on your current cylinder pressure, you may be able to move up a bit in camming. Not much room tho with the stock compression ratio and heads.