[LOWRIDER]

350cfm should work fine. 56 Ford 272 ran a Holley 94 carb w/about a 160 cfms. People tend to over do it picking carbs thinking if 500 cfms is good 650 will be much better. Your better off picking one with a bit lower cfm rating as opposed to the max the engine might tolerate. Personally I would choose the 2100. Simple carb to rebuild & tune but finding one w/a manual choke might be a bit difficult. But you could always convert the heat tube/automatic choke to an all electric choke cap. Just did that to my 4100 (4V), works fine.