A Mighty is not the right carb for your app. Most likely your idle/cruise will be pig fat...The mightys are designed for alot more cam than what you have.

I have a 825 mighty on a mild 440, cam has 20 more degrees at .050 than what you have. It was pig fat at cruise with stock jetting. In the mid 10s on a AFR gauge. Ive had to go smaller on IFRs and bigger on IABs and it is still fat at cruise, but getting better.

72 RR, Pump gas 440, 452s, 3800 lbs, Corked, ET Radials,. 11.33@117.72. Same car, bone stock 346s, 9.5 comp, baby solid. 12.24@110.