I'll be buying a 383 kit in the future, which means I'll have to upsize my carb. My question is which carb will work better, (sorry guys I'm really familiar with the Edelbrocks and I'd like to use the new Thunder Series), a 650 or an 800? This will be street driven only. No Strip. Some of my info is in my signature. Heres some more: RPM manifold, 1 3/4 headers, 228/235 dur. cam, TH-350, 2800-3000stall.
Now, every CFM calculator says I only need 621cfm to shift at about 5900 RPM, and have a 95% VE. The 650 Thunder Series would be more responsive around town so I think I'd like to go with that, but I'd like to hear what you think?

I'm running a 650 Holley on my 383 that I just put in my new car. IMO that's all you'll need as well for your plans.

I'm running a Holley Street Avenger 670 on my 383, throttle response is awesome!

Well thats some good news. Its cheaper than the 800;) . I wonder why they don't make any CFM in between those two. (Thunder Series). Oh well...

Why not run what you have now and see how it is, you can always upgrade later.

I thought a 600 would be a little small, according to that cfm formula. I could always give it a shot.

going alittle smaller is always better than going too big.

I couldn't decide what carb to use on my litle techno-resto 327 Elky, so it's getting a 1000cfm throttle body and Holley 950 commander / MPFI <insert huge grin here>. Been talking with guys running T/B MPFI, and Holley Stealth Rams, and I tell ya,, the technology is here for the hot rod community to sit up and pay attention. With WBo2 and standard fuel maps,, carburators are becoming a thing of the past.

750 vacume secondary all the way. The way it works is it only uses as much fuel that is needed unlike a manual secondary carb. There is nothing worse than getting a carb thats to small. Sure it will be super responsive on the street but your not going to get the max potential out of your engine. Give Patrick at pro systems a call and he will set you up and it will be ready to bolt on and run right out of the box.