The Corvette setup has a fast idle circuit, but no fast idle cam.
There is a rod from the manual choke lever that connects to a loose lever connected to the throttle arm. If the choke is pulled, then the rod pulls the loose lever, manually rotating the throttle arm/shaft.
I have seen these setups with the somewhat later (and much less expensive) marine YH units that originally had an automatic choke and fast idle circuit, with the universal manual choke caps replacing he original cap and bi-metallic spring coil.
The original Corvette carbs had a zinc alloy bracket that holds the choke cable tube, and breaks if you look at it cross-eyed. There was once a "huge" demand for these, but one vendor reproduced them out of brass, and they didn't sell. Making a mold for new zinc alloy was cost-prohibitive.
If I were going to do a set for a "driver", I would use the later marine carbs. Contrary to popular opinion, about the only parts that the Corvette YH carbs share with the later marine and turbo Corvair carbs are the bowl screws. Virtually everything else is different.
For years, there were no "correct" kits available for the Corvette units. The old Hygrade kit had the later (wrong) bowl cover gasket, wrong fuel valve, and for awhile, even the YF (mirror image) pump diaphragm. In the early 1970's, the Corvette dudes promised us faithfully they would buy kits with the correct partsif we made them available. We reproduced the kits, and "well, it is a stock item, I will order one when I need it, don't need one right now". Took us several years to get back the tooling costs. Learned a valuable lesson! Reproduce parts when you have paid orders, not promises.
Jon.
