Brian,

A gasket is not needed between the insulator plate and the intake manifold, but one will not cause any problems.

Be sure to align the slots on the inside of the carb-to-spacer gasket such that the slot is under a hole in the base of the carburetor (I hope that someone will post an answer with the correct terms for the slot in the gasket and the hole in the base of the carb).

If you use a gasket like this one, ...out alignment of the gasket to the carb.

Tim