33s will be a bit too much for that truck, most likely they'll rub. especially in the rear. i wouldn't fo any bigger than a 31 or 32 inch tall tire on that truck. You will need wider rims, a 15x8 speced for a '73-'87 4x4 or full size Blazer will do fine with the 31s, a 15x9 would be better with the 32s. As far as lug count goes, stay with the 6 lug.
