'67 Alignment issues after '74 Disk brake swap

[BMERDOC]

Caster IS NOT a tire wearing angle. PERIOD. The fact that he has no shims in the left side and "thin" shims in the right AND the camber is already .5° positive shows that NO MORE shims can be added to increase positive caster. Adding more shims to increase caster will only make the camber MORE positive. The lack of caster is the reason for the poor return to center. You will have to reduce camber before you can add any caster. If you are satisfied with positive camber (I wouldn't be) then you can mask the problem by doing the Caster mod.
Its time for pictures of the truck and suspension. Are your springs installed correctly? Are they the originals? What is your ride height?