Just from looking at the picture I can tell you your old jet was at least a 72.

You may be able to go smaller one or two jet sizes from stock, maybe more depending on your altitude. I'd start reducing jet size until you get lean surging at cruise, then go up one number. Holley says you have to make a two number switch to have a noticeable change, but on such a small carb I'd go one step increments.

I have bought jets on the 'bay but I have found a local place that'll sell me a pair of jets for $4.00. Some are new, some used...but unless some donkey messed with the holes, they work.

Another area where one can make the engine work better is ignition advance curve. Unless you have a problem with detonation, bringing it in faster will add some snap to the engine's performance.

R.