Looks like the total stack between the carb and manifold is about 9/16", two 1/8" insulating gaskets sandwiching a 5/16" plastic spacer. 1/8" seems kind of thin for an insulating gasket. Maybe they were more like 3/16" each and compressed some in the last 40 plus years.
There's a good selection of Stromberg spacers and gaskets at Dashman's Hot Rod parts:
https://www.dashman.net/