now, dont forget all cars now seem to have black, sooty looking tailpipes due to the "new" unleaded gas. You cant make the tailpipes "chaulk over" like they did on leaded gas no more. When swapping carbs, it is easy to have stumbles, and bogs due to the carb not responding to the signals from the smaller engine. But you dont seem to be experianceing any of those signs--although over richness would also prevent them. Over richness is sometimes a crutch/coverup to make a poor size swap work (at economy's disadvantage). JoeH is from good automotive stock-his dad is a famed Pontiac builder-tester guru. Good way to test whats really going on. I know that a 500 AFB is a dandy size for a 283 and have near stock 300 hp/327 AFBs (whatever cfm size they are) on 265s before with decent driveability. Remember the quote is "better hot than stock" not "better stock than hot" as a lot of old timers like to chime--I are old now, but still like the better Hot version best.
Also not to forget, even the 265s also came from the factory with twin WCFB Carters (and a bit of cam), but the 283s could be had at 245 hp with twin WCFB Carters and a SMOOTH idling cam. So I feel its not over carbed.
