brake problems need some help

HiThis problem is on a 1965 plymouth fury III its got power brakes worked fine. all that was done was put a elderbrock intake and carberator, headers, complete over haul. engine runs great but i have just a little brake at idle it has just enough to hold it but pedal gets hard. i have put a new brake boostrer and master cylinder.
do i need to put a vacum canister on it and if so what kind do i need. its a 383 automatic.
any help would be greatly appreciated. Thanks mike
Author: marblemike