Holley 750 (vacuum) or 650 double pumper or Thermoquad?
since you only got one shot..my 2 cents
3310-2 is a pretty old holley...might want to check on the throttle shafts to see if they are loose..also a rear metering block would be better then drilling the plate...
thermoquad...parts availability....????
holley 650 dp has my vote if it is a good carb....
since you say u got only one shot...choose the carb that is in the best shape...