What would be better for my new combo, 575 or 650cfm?

Hi Everyone,

I know I know, it's ANOTHER carb question....

Anyways, I've decided on a new speed demon vacuum secondary carb, but unsure as to which will give me better performance, a 575 or a 650.

My new combo is as follows:

289, 0.030" over

Performer RPM heads, 1.90" intake valve

Performer RPM Air Gap manifold

Cam (noticeably lumpy, I still don't know the specs)

Tri Y headers, 2.5" H pipe into flowmaster 40's

C4 automatic, 3.25:1 rear gear.

Well, my old combo I was using the stock 68 C code heads, Offenhauser dual port intake, and an old Holley 600 cfm 4160 carb. With the same bottom end and cam, I pulled 200hp at the wheels on the dyno. The old carb was tuned perfectly for regular driving, never bogged nor stumbled. It ran rich in the upper RPM's (5000+) Metering plates suck.

Can't comment on the performance now, because I'm putting the new heads on as we speak!