I'd think it'd be lean w/ 68-72 jets. I ran more in a mild 340 w/ a 750Hp carb. I'd look elsewhere for your issue. You probably want to start at 15* initial and 36* total all in full at 2200-2400rpm, then set your mixture screws for best vaccum. The holley 850 would be fine, you'll just have to tune it. Probably something like 72-76, 31 squirter.