Regrind Cam?

I agree with 72bluNblu on this one, I have a .030 over 340, KB 243 pistons, stock "X" heads using a Lunati 60403 cam, with LD 340 intake, 700 Holley DP, stock 340 manifolds and summit 2.5" exhaust and the car pulls approximately 15" of vacuum at 750 rpm.

So I would guess the vacuum is about what to expect from the camshaft in your engine.