32s and 30s are pretty common in 377 to 434 sbc engines with the 80A-1 pump. You need a small enough one for good pressure to assure atomization of the fuel but large enough to get enough fuel into your engine. A call to Enderle or Ken Shaw in California will get you in the ball park. Not knowing everything about your engine I would guess a 32 or perhaps a 34 might be more appropriate. Also fuel you are using. Gas uses much smaller nozzles than alky. Also the 80 pump comes in 3 sizes. 80A-1/2, -0, and -1. All flow different amounts of fuel and you need to know which one you have.