I'm building a 302 for my sister-in-law's 68 coupe while she's in Florida this next week. It is going to be 9.0:1 compression with stock 302 (circa 1978) heads. I will be running the Edelbrock Performer intake, cam, and carb (not the Performer RPM). Should I use the 500 cfm or 600 cfm performer carb? Thanks.