Accelerator pump, not the stall. As far as a stall, you need the right stall for the right build, and for racing you generally want a higher stall if you're going to be launching on sticky tires(it really depends on where the power is made). But your problem sounds like the carb. First of all even ported stock heads on a 289 with a little hydraulic cam aren't the greatest out there, given the lift of that cam it's safe to assume it;s not a huge cam, and with stock ported heads you're prolly only making about 300-325 at the crank. If it's a REALLY good build with REALLY good ported heads then maybe 350 honest flywheel horsepower. Peak power is prolly coming in somewhere around 6,000rpm, and you may be best shifting at around 6,500. What all this means is that the engine isn't moving anywhere near 750cfm, prolly more like 550 cfm at MOST when at peak rpm. And unless you have a custom built 750cfm you're going to run into problems. Most of the off the shelf type carbs are designed around general applications and aren't terribly expensive, so they don't meter as well as the uber expensive custom jobs(ie they don't use badass booster and emulsion packages). A typical Eddy 750 for instance is going to be set up for WAY more engine than you have, jetting will be wrong, accelerator pump will prolly be way off(reason for your stumble) and it most likely is costing you power throughout a LOT of the RPM range from ineffective metering. You at the very least need to dial the pump and jetting in, but in all reality you'll prolly find you'll go down the track faster with a smaller carb. You also have to have ignition set correctly. Right timing, right plug heat range, right plug gap. If ignition is off then the carb is off, like the old saying goes - 90% of carburetion problems are ignition problems. Carbureted applications can be VERY fickle, even if 1 thing is just slightly off it can be a real pain.

 

A 289 is grossly overcarbed with a 750, you should use a 600 or 650 max.
The loss of vacumn from too big a carb is hard to overcome with the acc. pump shot.
Recurve the distributor for 10 deg advance = 20deg @ the crank.(all in by 2500 rpm)
Set base timing @18 deg. (for a grand total of 38 Deg adv).If she pings on you, use higher octane fuel, or retard base timing 2 Deg.
Accelerator pump linkage needs to be adjusted to have ZERO slop.
The smallest movement of the accelerator should have fuel squirting into the boosters.
True stall speed is rated with a transbrake. Not foot brake, so if your car doesn't have one, use a looser convertor.3500 stall should work for you.
Lose the 3.55's( you did say it was a racecar didn't you.)
With a 28" tall tire you should have at least a 4.10 gear(4.30 or 4.56 would be even better) if you don't street drive it much.
The only way the motor will pull to 8000 rpm is with a solid roller cam.
Don't forget a stock bottom end will come completely unglued @ that rpm level too!
6500 rpm sounds more useable to me.

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750 edelbrock. There is one of your main problems. Get a Holley.

And just for input I turned my 1968 model block, crank and rods 8K rpms for over 10 years with 250HP of N2O on it. Now when it let go it broke two rods. But 6 are still usuable. I ran a solid roller, TFS heads. Cam was 688 lift on intake and 644 on exhaust. It ran 10.50's in the 1/4 @ 127.