Are they already disc brakes or are they still drums?
I don't want to assume you already converted to disc because there will be a big jump in performance from manual drum to manual disc.
Getting a booster installed is pretty difficult on a V8 even a 302 if the engine is still installed. You have clearance issues, new hard lines and a new brake pedal to install. None of those problems switching to manual discs.
So if you don't already have them try the manual discs as an incremental step. Nothing you do will be wasted if you want to add a booster later.