I think 1969 was the last year for the 6 bolt lug pattern for the old chevy half ton trucks.
I'm pretty sure the '73-'87 were five lug wheels in half ton, except for the 4x4 trucks which are designated as K models. The K models retained the same 6 lug pattern as the earlier trucks. I've read of guys using the later model 4x4 wheels on their older trucks.
So, if you want to use the rallys, you need to look for 1967-1969 model in 6 lug.
-W
