Having alignment issues (caster)

[Tahiti or Truck]

I have a 66 C20. While at the junkyard gathering stuff to convert it to power steering I stumbled across a 1976-77 ish GMC Sierra grande with big 8 lug disc brakes. I went back the next weekend and pulled the spindles, rotors, tie rods ( and sway bar). I read that I had to replace the ball joints to that year which I did.

It all installed ok and I took it to the alignment shop and they told me I needed one degree offset upper control arm shafts. Stating that there is no adjustment left because of the spindles not have caster built into them. So 544 dollars later I get the truck back and notice a bad over steer that progressively gets worse the faster you go....as in kind of dangerous I called them and they said that it's probably my steering box and that I would probably have to pay them to replace that too. .bull ****! Anyways. I am pretty confident that it is a lack of caster causing the problem. There is one shim in the rear control arm of the drivers side and no shims at all on the passenger side.

Like I said, scary oversteer...that you have to counter steer and the wheels do not come back towards center if you let go of the steering wheel after a turn.

My long story short.... Do the upper control arms off of a 1977 C20 have caster built into them? More so than the stock 66. I ordered a long acre bubble alignment gauge so I ll know in a couple days what my angles are.