Jon G. - it can be MUCH worse than you indicated.
On certain models, the "rebuilder" will identify ALL vehicles using, say a Carter AFB for a Pontiac. Pontiacs have similar throttle arms on V-8 engines (326, 389, and 421) from 1959 through 1967. The rebuilder would then determine the RICHEST calibration (generally for a 421 with automatic and air conditioning), and any vacuum take-offs that would be necessary for any of the 50 or so different carburetors included in this group.
The disassemblers would disassemble a few hundred of any of the group, grouping parts as you mentioned, and cleaning.
Following cleaning, vacuum tubes would be installed in each casting.
The units would now be assembled with the RICHEST calibration (determined above), and the units would be sold under a single rebuilder's part number.
So a customer goes into a parts house and asks for a rebuilt carb for a 1961 Pontiac 326 with standard transmission " oh, that takes part number 4-607 (or whatever)".
Another customer goes into a parts house and asks for a rebuilt carb for a 1965 Pontiac 421 with automatic and A/C "oh, that takes part number 4-607 (or whatever)".
The listing in the "rebuilders" parts book would be "Pontiac V-8, 1959-1967, all, except SD" - 4-607.
In a different lifetime, when we were still restoring carbs, we used to figure, on average, we could disassemble 10 "cores" of the exact same model, and have enough correct castings to do 6, 7 if we were lucky. Since Carter, and to a somewhat lesser extent, Stromberg, were always our specialties, we have literally thousands of left-over castings (air horns, throttle bodies, venturi clusters, etc.) that we identified and saved.
Jon.
