Chevelle pulls to right....need advice

[SS4Real]

No teenagers at home to blame yet. My little guy is only 6 so if he's been sneaking out to race at night for money, I have lots of sleepless nights to look forward to!

Seriously, to answer some of your questions. Yes, it was parked with the parking brake on (manual transmission). As a matter of fact, I had the power booster replated and reinstalled as well as the parking brake adjusted just before winter set in. Now, the rear brakes will sometimes lock up when you apply moderate pedal pressure (front discs and rear are drums). I thought that might be a proportioning valve issue, but it's my understanding that my car does not have an adjustable valve. I remember reading somewhere that some Chevelles do have an another valve on the frame rail on the drivers side. Maybe this is all related. I feel like I'm chasing gremlins sometimes. Yeah, I know. This is fun stuff.