History: The original 780 Holley came on the 425hp 396 chevy motor.
Meaning: Your carb is the right size for the engine.
Constraints: You want to keep it an Edelbrock carb.
History: Many, many 750 Edelbrock carbs have had problems and yours hasn't, at least you have been driving it for years, so you have one of the ones that work.
Solution: Fix the carb you have. There have been no developments in the Edelbrock carb lines since their version of the AVS came out.
Alternative: 800 Thunder series if you just have to have a new carb.

R.