My $.02 thrown in. I'm in the process as of now (slowly) of installing Street or Track UCA, lowered 1". I know from reading the how to's on lowering UCA they say at least with stock arms is to remove 3/16-1/4" of shims equally as a starter. I know that GW includes a spacer. I would follow their initial settings on shims if any. According to the Ford shop manual on 65-66 each 1/32" shim is good for 1/3* camber or 1/2* caster and not to exceed 1/16" difference between shim packs. This would mean a maximum of 1* caster possible. Maybe make all the shims, divide them into 2 equal stacks then subtract 8/32" from one stack and 10/32" from the other. The stack with 10/32" would go in the back and the stack -8/32" in the front. This theoretically would be the same as removing 1/4" plus an additional 1/16 in the rear and 1/4" in the front to give you 1* caster difference and be able some what to drive to a shop.
I'm not a complete idiot, pieces are missing.