I need help w/a brake problem

[SCOTI]

I swapped discs on to my 68 beater over 2yrs ago & they worked great. For the swap I used a 71-2 pwr booster/mstr cyl combo & the lines, pro-portioning valve, & hardware are 73-up.

Ok, here's the problem . . ... last Sept, I was in a wreck while pulling my car trailer. Of course, during the wreck I panic stopped (the trailer brakes weren't hooked up) & locked up the brakes.

Since then, it's like I don't have rear brakes. At first, I thought the shoes were just worn down/out of adjustment so I replaced & adjusted them but that didn't fix the problem. Then someone said they had heard about panic stops causing the prop-valve to 'stick' & cause this dilemma on Chevy trucks so I got another prop-valve @ the wrecking yard & re-bled the brakes but the problem still exists.

I'm tired of my front brakes locking up whenever it rains because the backs aren't working. Any suggestions??