What size spacer best for heat soak slant 6 Carter

There's a guy on feebay (a regular member on the /6 site as well) that sells a phenolic spacer for a BBD that's about the same thickness as the "thick" fiber gasket that used to be used with these carbs as stock. He's "badvert65" on the /6 site, everything he sells on feebay ends in "$xx.65". (the partial dollar, the "change" part of his price is always 65 cents