A 350cfm carb would put you right where you need to be. On PAPER a 292 at 4000rpm would pump 338cfm. With that intake have you considered using a self tuning TBI? We don't use carburetors anymore and everyone has been very satisfied with the result. An O2 bung in the exhaust, high pressure fuel pump, and very simple wiring is required. Zero hot-cold starting problem and MUCH better economy.
