I cant seem to locate a base gasket

[Gumby]

any substitutes out there?

Racers back in the day and for many years I ran plywood carb spacers.

Last time I made one, I used A/A sided outdoor signboard plywood.
[what you buy at like lowes, is C or D sided, very rough and pouris with lower quality woods and would not last.]

course now you can buy high quality plastic and make one from that. Every town has a place that sells plastic n sign board to supply sign shops n such.