[davepl]

500 is plenty. If you've got a spread-bore or dual-pattern intake I'd put a Q-Jet on it. Helps if you have someone good at tuning them, but there are only 3 living people left that can do it :-) Otherwise I've had good luck with the Edelbrock (Carter style).

Your open element air filter will make cold start drivability more problematic, but as long as the choke is set right you shouldn't have to two-foot it (my pet peeve).