I’d look into a chassis dyno in your area........ tune for power....... bring the old main body with you, and some notes on how to put that carb back how it was when the car went the quickest/fastest.
In fact, that’s probably the place to start.
I’ve tested a number of home brewed carbs on the dyno over the years....... some have been so far off(both from a power and/or fuel curve standpoint) that no amount of jetting or air bleed changes were going to fix it.
They needed more reworking than that.
The best luck I had with building a carb from readily available parts was the original Proform HP 750 body, using stock Holley 4779 metering blocks and a plain Jane 4779 type baseplate.
I built a few of those, and they required minimal tuning to get dialed in.
I built a similar carb with a Holley HP body, QFT billet metering blocks and baseplate.
I haven’t had a suitable candidate on the dyno I could use to dial it in....... so at this point, it’s still an unknown.
When we were selling BG stuff, and the Demon carbs........ I found the calibration of those things to be properly set up for.......almost nothing.
The Speed Demons in particular always seemed to have idle, driveability, and wot fuel curve issues.
Often all three!!
It got to where if I was going to be using a new one on the dyno for a build we did, I’d just modify them for adjustable air bleeds before ever being run.
By that time we had a better handle on what changes to make to the baseline calibration so they’d be closer to “right” from the start.
Some of those things as they came ootb were particularly bad.......they’d hardly even run.
Wouldn’t idle, super lean at wot, headers start glowing right away at part throttle, etc.
But......they looked good.
Eventually, it just got to the point where they were just more trouble than they were worth........ and we stopped selling them.