Holley Jetting question

Check out mcmaster-carr for the parts you need to tune the carb

brass set screws in 6-32 and 10-32 threads
tapered and bottoming taps same sizes for modding the metering block.
Drill sets in 1-60 and 61-80 sizes

As 19dart66 mentioned, find some wire and put it in the holes to get a general idea of what is needed to reduce an existing opening. Get used to the formula, pi times radius squared... It's required to figure out the area of the opening. A common misconception is if you have a .050 hole and you stick a .020 wire in it you now have a .030 sized hole... which is VERY wrong.

Since you have an AF meter it should be easier for you to get a handle on it.