The proportioning valve should fix the front/rear split. On Impala SS's there was what was referred to as a "stealth bolt" mod where guys would add a piece of bolt inside the proportioning valve to direct more pressure to the rear. I think the 4 wheel disc master cylinder adds more pressure to the calipers. If you don't have to push too hard on the pedal to stop, then I guess you are OK.
So Ms. Vanessa is your car's name? I call my 56 Ford Fairlane Victoria Ms. Vicky. "Victoria's Secret" is a small block chev. driveline. LOL