Both Back Tires Crooked?
 

Hello there! Got a truck full of unicorn problems that no one can figure out!

1997 Ford Ranger, 2.3L, Manual, 4X2

Went in to align my truck/balance my tires/have my suspension checked and found out that both my back tires are steering to the right. What I mean by this, is the Les Schwab said they couldn't do anything about it no matter what they tried.

When driving straight it steers hard right, so I have my wheel cocked to the left permanently and when I hit big enough pot holes, my entire backend goes to the right. Bad enough that at 70mph there was a dip in the road that I hit, fully braced and ready for it, that drove me into the lane to the left of me. I was physically unable to stop it from happening. Les Schwab said it wasn't bad enough to wear my tires down in the 3k miles i have driven on them however. Anybody know what could be happening??

Bent frame maybe, frame can be checked with laser measuring at a shop
I assume this Ranger has not been in any accidents, that you know of, in the past, i.e. title is clean not "rebuilt" or "salvage"
Bed doesn't look like its been replaced?

The leaf springs hold the axle in position, square to frame
The leaf springs have rubber bushings that hold them to the Hangers
Check if bushings on front and back of each leaf look OK

The hangers on the frame hold the bushings, make sure they look OK