Um…like…holy snot! I coulda sworn there were two of 'em. Maybe I was conflating a dual-carb setup marked by some aftermarket outfit or other in the '60s?
Corvair had two 1 bbl downdraft carbs on the base motor. One on each bank. The "spyder" used the Carter YF sidedraft on the turbo, as shown. What many don't realize is there was no "boost control" as used today. Boost was regulated by turbo size, intake restriction (1 bbl carb), and the exhaust system design. By removeing the muffler, and installing a adapter with a 2bbl carb, boost could be raised from approx 7 psi to about 10 psi. My 65 Valiant 170 has a Corvair turbo with some mods to the compressor housing to allow for a "standard" 3 inch inlet. Even have the Corvair exhaust pipe.
PS: Cobwebs are in the way, but I think there was also a OEM four 1 bbl Corvair setup.
EDIT: just checked my book. 1965-1966, four 1 bbl carbs, 140hp at 5200 rpm