The carb doesn't know what size of an engine is under it, all it knows is the velocity of the air going through the venturis and especially the venturi boosters. As the air flows through the boosters it speeds up and because of Bernoulli's equation we know that pressure at that point drops.
This pressure, which is below atmospheric, allows the atmospheric pressure plus the pressure of the height of the fuel in the float bowl to push the fuel through the jets and boosters into the air stream. So what the carb reacts to is air velocity. Period.

It stands to reason that a carburetor set up to provide a correct air/fuel ratio over a wide flow range will do so on various sized engines. This is the long way of telling you that if the carb is set up right in the first place you shouldn't have to rejet just because you put it on a smaller engine. Air velocity will be quite slow and you may need to adjust your accelerator pump shot because small differences in throttle will produce small differences in fuel flow that might not keep up, although that's an area that you have to experiment.

The front two barrels of a 3310 750 Holley are about the same size as a 500 cfm Holley two-barrel. I suspect you will not be seeing the vacuum secondaries open very often.

But I suggest this talk of "jetting down for a smaller engine" is out of widespread ignorance of what the carburetor actually does. I suggest you stick the carb on and see what happens. Use the non-stick gaskets so jet changes will be easier when you start experimenting.

The other question is why you think your Edelbrock carb is junk. Did you break it somehow? I bought a carb that someone had turned the idle screw in so far that it broke the casting. I don't know how to fix that! But almost everything else can be repaired or replaced.

Edelbrock settings for carbs are easy to replicate as their info is all over the Web. Their electric choke carbs are lean for mileage, their manual choke carbs are rich for power. They are easy to change and the charts tell you exactly what to do.

Good luck!
R.