Mitch,
Do you have the specs on the engine? (compression, cam, intake port volume, etc)
I had Pro Systems build a Holley for a 422 SBC I built and it was bang on.....right out of the box. A/F ratios were right on during the dyno test, it was VERY drivable, and proved to be a bolt it on and forget it.
It was worth every nickel over the standard Holley.
https://www.prosystemsracing.com/
Tim