Ok, one more question on the Holley jetting.

TrailBeast said

The transitions show near a perfect square

Click to expand...

Square was never a specification. It was always a ballpark description for a quick check and for guys who had no means to measure. You are absolutely free to give the idle position screw another 1/8 or quarter turn. Then reset the idle mix screws to trim the idle mix.
It's a free experment (other than burning fuel).

The other thing you could do with the carb off is measure the t-slot width and length to see if its relatively normal (old school) or extra long or wide. Being a Holley my hope is that its in the range established back when millions of carbs were going into new cars.

The range of exposed under the throttle for an old school carb was expected to be .020 to .040" see Mike Urich's Holley Carburetor's and Manifolds