Been using narrow band O2 for tuning since the late 80's, the gauge tells you all you need to know. Just work on it circuit by circuit and they run like a top in no time flat.

I think in the early 90's I was given one of the new aluminum Holleys to play with. A LOT of time was spent trying to get it right, it was incredible how crude the fuel circuits were and rough the transitions were from circuit to circuit. Had to drill the shooters and adapt a 50 cc pump to get rid of a lean spot on the primary side. The thing would go from full rich to full lean on the gauge in a heartbeat, there was almost no in between. I think the Holley strategy was to just have it "run rich" all the time to cover the transitions, stands out like a sore thumb if you have the tools though.

Still have it hanging from the garage wall.

I'm willing to give the 780 I have a shot as it is only a couple years old and perhaps Holley has made some strides since the 90's on calibrations and circuits.