If your just doing a 4bbl swap and buying new and don’t plan on other upgrades then a 500 cfm is probably all you need. But I don’t see no reason the normal 600/650 cfm wouldn’t work.
I was thinking about a replacement for my original carb and bought this 600 (with electric choke) at a swap meet for $100. It works perfect. It was like new. The guy bought it and went with a bigger carb.