I have a '49 3100 which has a 350 in it and the CPP power steering kit on it and started out with the stock caster shims (1.5 degrees I believe). The truck made no effort to go back to the straight ahead coming out of a turn whatsoever. I bought a set of 5 degree shims and it now comes back to the straight ahead position better. I think that 6 or 7 degrees would bring it back to straight even better, but if you go that far, you'd better have brand new, tight spring shackles and pins.
With the 5 degree caster shims, those spring shackles and pins receive a lot side torque on them that you can see while someone turns the wheel for you when the truck is stationary. I think i'm good with the 5 degree shims.
