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Edelbrock Thunder Series 800cfm, with the AVS or air valve secondary's the engine only gets as much air it needs despite your best efforts to push the gas pedal through the firewall
It really depends on what rpm you want to run. if you stay below 5000rpm, then the 500 should be fine. The smaller carb will usually have better throttle response and mpg. if it is running good, I would leave it alone.
As a comparison, my old 77 had a 460 with a Performer intake, CompCams 268h cam and headers and ran fine with a 600 carb. It ran about the same with a 750, so I kept the 600 on it when I sold it.