The CFM won't be different, but there are internal differences. There is also no difference in the venturi size. Both have a primary venturi of 11/32" and a secondary venturi of 11/16" and a main venturi of 1 5/16". Both used a .81 fuel orifice. For the differences: The 966 used a low speed jet tube of .032 inch and the 2100 used a low speed jet tube of .028 inch. The bypass in body sizes also differ: 966 is .0635" and 2100 is .067". Economizer sizes...number 55 in the 966 and number 54 in the 2100. The metering rods are different. 966 is...economy step .073", middle step tapers to .059" and power step is .050". 2100 is .067", taper to .060" and .050" for power step. Metering rod jet for 966 is .1015" and for 2100 is .0945". Those are the notable differences. Hope it helps.
















~ Jon
1952 1/2 ton with 1959 235 | T5 with 3.07 rear end