What aftermarket carb should I get?

[GMC1970]

I have a 1970 2500 with a 350, edelbrock performer intake and vortec heads. The previous owner disabled the choke on my quadrajet and with the edelbrock intake, I cant rebuild the factor choke anyway. I was leaning towards a 600 cfm holley 4160. I have stock headers. Does anyone have any opinion based on my vortec heads and performer intake, 600 should be a good fit? Any opinion on the 4160? I used a few carb calculators, but I was not sure if vortec heads and performer intake make a big enough difference to require more than 600 cfm?