Rear brakes locking up to fast

[RichardJ]

>>When I freshened up the truck last year I replaced "all" braking components<<

>>a recent aggressive braking action brought it to my attention. The rear shoes are nearly worn out after just 8K miles.<<

That clearly sounds like Lee H can determine the difference between new shoes, worn shoes and contaminated shoes.

It is possible the shoes were flipped rear to front and went unnoticed, but the short shoe on the rear would have all the wear and the long shoe on front, would have considerable less wear. That would have raised a flag.

I think crimping a brake line, breaks down the lining and isn't something I would consider.
Find a dirt road and see which wheels don't lock up at different brake pressures.