Hello
I believe what you are looking for are the thick phenolic (like) gaskets that go between the cylander head and the base of the intake manifold.
I got mine at Pelican parts recently, others may also sell them.
Here is the link for a 73 to 76 part.
http://www.pelicanparts.com/cgi-bin/smart/...2C%20Each%20%20Be prepared to take Zack's advise with regards to making flat the bottom of the intake manifolds. A good straight edge across the mounting area of the manifold shows the problem.
The gaskets you are asking about are thick, made out of a phenolic kind of material and wont conform to the irregularities in flatness your manifolds might exhibit. In other words, they dont squish!
I have not actually mounted mine yet and at this moment I do not recall what kind of gasket goop (if any) you are supposed to use. Maybe Zach or others might chime in here on that one.
Im doing mine this spring also. But I did see first hand the manifold flatness problem back when I rebuilt my carbs.
Also, the carb experts (Mark Harney, John at Aircooled.net) over on Samba related that many of us seem to apply way way too much tightening torque to the manifold bolts.
I wish Id written that torque value down when I came across that nugget of info. I'll have to search for it again over there at some point. Maybe its just the same torque that the FI manifold gets, I dont know.
Anyway, have fun.
Curt