Help me pick a new carb

I didn't know you had a automatic trans in the car. That knowledge and your gear ratio & tire size should have been disclosed to help make a better educated suggestion.

The same engine combo in two different cars could get two different carbs. Here's an example.

Car one has a stock 904 & 3.23 gears with a stock sized tire. (Or close to it)
Car two has a shift kit and a 3000 stall converter, 4.30's a d a 27 inch tire.

IMO, the top car gets a 600 vacuum secondary carb.
Car two gets a 750 double pump.