I've spoken with a couple re-manufacture companies. They think the heads are exactly the same from 97-07. They checked AllData and couldn't find any differences. When I told them the below information about the heads in my hands, they said the one's with the 1.83"; intake valves must be aftermarket. I checked the 2 sets of heads I have and the L67 do measure 1.8"; for the intake and the L32 measure 1.83";. Both heads have a cast# of 4781 and the exhaust valves both measure 1.52";. I spoke with Eric of Morad and he says they're the same head, just the L32 have the larger intake valves with a different angle seat cut to seal better. Does anyone know where some of this information can be referenced? Did GM keep the same cast# but change the flow design?
