Swami, JW has it right - the 965S has the smaller bore and narrower bolt spacing for the 216 manifold. If you can find a 966S, it has manual choke and the same wider (235 manifold) bolt spacing as the 2100S.

Here is Jon H's article from his website that shows the long list of Chevy-spec Carter YF carbs: Carter Type YF Carburetors Produced for Chevrolet.

Doug


1947 2nd-Series GMC FC152 3/4-ton
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1953 Chevy Bel Air Sport Coupe Powerglide