Thread: L67 vs L32 Heads, casting #, how to tell the difference?

I've heard from different vendors and seen on Wikipedia the L32 Heads have a better flow design and 1.83" instead of 1.8" intake valves on the L67 Heads. I also saw on fullthrottlev6 the L32 exhaust valves are sodium filled. For these reasons, I was trying to purchase a set of used L32 heads, but after a month a recent deal fell through which I'm still awaiting a refund.

I decided I'm going to buy a set of remanufactured heads. Most the parts stores have the same part # if I look up heads for a 1998 or a 2007. Some stores like Advance Auto have the same casting # listed for both years as well of #4781. Some like NAPA have different head castings available, but I don't know what years the head casting #'s relate.

Is there different head casting #'s for L67 and L32 Heads? If so where can a list be found? When Heads are remanufacturered, are they using the heads and valves found on the newer designed L32 or are they just taking both L67 and L32 heads and putting the same part # on them so you don't know what heads you are getting until you measure the valve size? To me that would make a running problem if one of the heads you receive has the 1.83" intake valves and the other has 1.8" intake valves.
Thanks for any help.

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?

the only difference is the intake valve being slightly oversized on the L32 heads. the casting themselves are identical.