Even easier... The original 3310-1 was a holley 780 Vaccum Secondary Carb. It was different than other 750 Vac Secondary carbs by the same number because it contains a second metering block in the rear of the carb, when the newer style Vac Secondaries simply act with the small metering block inside the bowl. If the carb has the second metering block, it is a safe bet that your carb is a standard 780, which was original equipment on some old chevelles, camaros, mustangs, torinos, and even a handful of Ford pickups, incase you are looking for replacement parts.
Hope this helps