I just opened up one of my junk carbs. The main jet thread is 1/4-28, same as a 1/4" National Fine thread bolt. The Holley jet rethreads very nicely by running it into a 1/4-28 die- - - -I just tried one. It looks like A Holley #56 or #57 jet should lean yours out a little. If you have access to a lathe and some number drills, you can turn out Rochester jets by the dozen by machining a piece of 5/16" brass rod. I just might set up my lathe and build a few for myself!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!