I wonder if anyone could tell me what's the correct amount of vacuum in inches the brake booster requires to make it work? I have a built 327 which is only pulling around 8" of vacuum at idle and has no power assist with a hard brake pedal feel. Would an electric vacuum pump cure this problem?

8" of vacuum is pretty low for power brakes. yes a pump will definitely help , but you may try a vacuum canister first they are allot cheaper and should solve the problem.

A vacuum reserve canister was the first thing I tried and did not help.