Are you talking about the thick gasket between the intake manifold and the base of the carb ? If so I should have the part number at the shop.Pm me and I will get it for you.
The carb base gasket is a Fel-Pro #60085 or #13-1026. The factory gasket is much thicker than the replacement but works fine.
Darter6 -
You could stack 2 gaskets, it may help.as I said the replacement gasket is thinner that the original. Do a search for "slant six fuel line modification". If you don't find it here check out "slantsix.org" or google it.Some say it cures the problem.