Those shims adjust the caster. You want the kingpin to tilt back slightly, and using wedge shims between the axle and spring is how you adjust it.

You need to assemble the truck and check the alignment to know for sure whether you need one or not.


1955 1st GMC Suburban | 1954 GMC 250 trailer puller project | 1954 GMC 250 Hydra-Matic | 1954 Chevy 3100 . 1947 Chevy COE | and more...
It's true. I really don't do anything but browse the Internet looking for trouble...