You didn't state what fuel you are using, and didn't complete the pump information, as 80A-0 -.5 or -1. Make a big difference. Call or Email Hilborn, and they will give you a ball park starting point, just convert your Enderle pump size to Hilborn pump size. They will give you a "on the rich" side cal, because they really don't know the exact flow rate of your pump, just a ball park figure. My guess would be 9A nozzles for gas, or 20A nozzles for Alcohol. Don't know what barrel valve you have, gas alky or nitro, I use a nitro barrel valve on alcohol with a injected motor, with 18% to 22% leakdown. If gas is the fuel then 9% to 10% leakdown. the return pill size depends on the pump size. Don't worry about a high speed by-pass until you get the basic fuel cal worked out, then you will richen it up a little and work with a high speed by-pass. Since your system wasn't tuned on a flow bench, your will be spending a lot of track time tuning it. I have put a pressure gauge in the system and found out what pressure was at around 6500 to 6800 rpm's then set up a high speed for that pressure with the main jet richened for the high speed install to the system. Just make sure you keep a eye on your oil for fuel contamination. If I remember right on a Big Block Chevy, Number 2 cylinder is the one that has a tendency to run lean. Jerry