You'll get many good replies on the gasket sealant question, but my first suggestion would be to call Moss Motors and ask. If they say yes, then ask what sealant they recommend.
Another thing to check when you start the work - is the carb to manifold junction surface flat (not warped), to allow perfect mating of the surfaces? I had a major vacuum leak due to a warped (heat?) carb base; had to true up the surface by rubbing across sand paper on a flat steel plate. My brain has failed - can't remember the word for that process.
Tom