Take off the air cleaner and check the numbers stamped on the choke horn. post them here and I can tell you pretty much exactly what it is. Hopefully (I'm assuming it's a drawthrough) it's actually a 500cfm 2 barrel, as a supercharged 1.2 (let alone a 1.5) could really use the extra cfm.

If the choke horn has been machined off, flip it upside down, and measure the diameter of the throttle plates, and the carb size and model can be determined by that.

Hopefully it isn't a 320 holley, as they were made basically starting with a 350, but designed to run leaner (and they end up flowing 30cfm less as a result) with more sensitive boosters - they are basically an emissions friendly carb, and less performance oriented. The idle circuitry is also different, and the idle mixture (from memory) is adjusted the opposite way (i.e. the way the idle screws are turned to richen a 350 will lean a 320).