I am trying to determine what carb to replace the existing one I
currently have. The racing I do is Autocross which requires that I do have to down shift at times in order to come out of a corner. Currently I am having a problem that when I do down shift the motor is getting flooded out and at idle the motor is loading up on fuel. I have had the carb tuned so many times that it is hopeless not to mention changing of jets more times then can count. At this point of doing a complete rebuild may cost more then a new carb. I am legally limited to 650 CFM rated carbs in the class that I race. This car currently runs on 100 leaded octane and will never see street use. I have included as much information as possible about the motor.

Chevy 350 2 bolt out of 1973 El Camino
bored 30 over
10 compression
Sportman II heads 64cc chambers 200cc runners 2.02/1.6 valves Max lift .560
headman Headers Long tube into true dual exhaust
Edlebrock Performer RPM dual plane intake with .7 carb rise built into
the
intake (1500 -6500 rpm)
.5 carb spacer
March underdrive pulley
Fluiddamper harmonic balancer
Comp Cams Extreme Enegry Flat tappet 290H
290 in/306 exh 250/256 @.050 .519/.523 Valve lift 110 degrees
Scorpion 1.6 roller rockers
Comp Cams harden push rods
ERson timing gear
Mallory distrubutor mechanical advanced locked out at 36 degrees
Mallory high energy coil
Mallory electric fuel pump and filter
K&N 14" beather with K&N beather lid
MSD rev limiter box with 6400 pill
Engine Revs to 6400 with no problems
4.10 rear end gears
Turbo 350 automatic tranny
B&M stall convertor 2500-3300 stall
Ray Sissons
2003 Black Z06 50th Aniversary
SPOKES 85 Z28 CP #13

What carb are you running now?

Reduce the fuel bowl float height to a minimum.
As long as the carb is not starved for fuel its high enough.

Get spring loaded off road needle and seat assemblys
use smaller needle and seat assemblies (the bigger the N&S assembly the harder it is to control fuel level during cornering)
reduce fuel pressure.
Install fuel bowl vent whistles
Install a hose connecting the two bowl vent tubes and cut a breathing hole at the top of the arched hose. tie wrap the hose to the carb stud. (this will keep the fuel from flooding out the vent tube during an sudden stop or start.)
Install jet extensions front and back and use the slotted floats for
jet extensions.
remove the carb and reset the throttle blades position at idle.
ballanceing the front and back barrels.
the transition slots should be just exposed under the blades
on all four barrels.

If you don't have a functional PCV system hooked up, hook one up and vent the other valve cover.
If a holley carb has a 3/8" vacuum port at the back base of the carb, it is designed and calibrated to idle properly with a functoning PCV valve setup . Othewise the whole idle circuit will be over rich and the throttle blades will not be positioned right at idle . (you'll never get the idle or off ide response right.)
Car will tend to load up over time.

the metering blocks may be leaking fuel or pourus.
A new carb could just as easily have the same problem.
Check the gaskets and mating surfaces for warps or scratches etc.

Holley double pumper 4777-2 It currently has the vent exstions.