Available power valve plugs would be the easiest option.  If you’re talking about the four slots in a power valve, then yes, you could potentially lead in the holes to make your own power valve blockoffs.  I’ll add that power valves holes do vary as some have a different number of slots or windows while others simply have holes of varying sizes.  If making your own power valve blockoffs out of old power valves, then make sure the gasket surface is true when finished.  When using any kind of power valve plug, a little blue loctite on the power valve threads along with the gasket will insure that no fuel seepage past the threads occurs.

With the blocking of the enrichment channels within the carb, the jet sizes in the end carbs should be increased.