I can get, or used to be able to get, teflon gaskets from Dave's Discount Motors. They were about a quarter inch thick if I recall correctly. I still may have some for my Baja 5B. As far as the mount screws, I don't recall there being a second set to mount the carb to the intake.

Does it really make a difference? Its easy enough to make two sets, but I just can't see that much heat coming through the screws. I'm not 100% certain, but I believe on the Baja series cars the carb and intake bolt on with the same screws. They seem to run fine that way.

Mind you, I'm not trying to say its wrong or whatever, just what I recall of my Baja goes against that advice.