Hey guys I'm looking into a new carburetor and not sure on what cfm size to choose. I have a 1967 400 with an 068 cam, 670 heads, edelbrock performer intake, and 4 speed muncie. Currently running a tired edelbrock 600cfm and car runs fine but not sure if that's too small or I would get better performance with a 650 cfm or 750 cfm?