I'm topping off motor now and my airgap and heads don't seem to be close enough to make a good seal on the intake to head seal and when the oil galley gaskets are in place, cork or rubber it gets worse even w/.125 thick intake gasket and I'm afraid to torq down the intake and break it. Is there something I'm missing? Plus all the gaskets I have all have the mount holes coming into the heads from angle side or mating surface side not the top as is required by the airgap intake. I have the 4516 intake and 12464298 heads any help would be appreciated.

Was the block decked? The heads milled? That would lower them in relation, and spread the gap farther apart. If it has, and you know how much, you can have the intake milled down to match.  

I believe that those fast burn heads have raised runner intake ports so youll need an intake to match...also I believe the rpm air gap number is 7516 for vortec style heads.

Im not sure if youre just having a regular compatability issue..but thats what it sounds like.
10051103 is the GMPP manifold that will work with those heads.

Hope that helped

Good luck and God bless
-Shred

Thanks for the reply I had the numbers wrong, I do have the 7516 and I will have to get with my machine shop and have him come up wth a solution but what kind of intake is that shred? Obviously G.M.P.P. I'll do a little research and answer my own maybe thanks.