Pulling V.A at idle

Mattax said
With a Holley 4150/60 set the initial throttle position as shown in the post above here:
Large RPM and Vacuum drop when shifting from park to gear

Tuning for performance procedure outlined here Setup for 750DP on this 408

Ironracer said
No Sir, the Lil flat head ones behind the float bowls. Primary sides only... fuel/ air mixture? Standard starting point is 1.5 turns out bottom, usually... ? At least that's what Grandpa told me

Yup. We're on the same page. What caught Mike's attention was the 3.5 turns out. That's an awful lot.
If you caught it above my suggestion was the same as your Grandpa's. Then when warmed up, adjust by turning in (leaner) until it looses rpm. Then turn it richer. Much easier to detect performance drop going from rich to lean. The reason to turn it richer once that point is established is because the test was in neutral and with load the engine will need a richer mix.

Ironracer said
I haven't messed w/ the secondary blade adj... it's outta the box, 12 years old

Great! So now if/when you crack them open you can keep track of how to return to factory. That's by taking notes on how many turns or fractions of the stop screw.

Same concept with the primary throttles. With the carb on the bench, measure the transfer slop length visible below the throttle plates when the idle stop screw is just touching. Then note how many turns it takes to open the throttles so .020 .030 and .040" of the slots are revealed. This way you will know how much the transfer slots are exposed by counting the turns on the idle speed screw. Saves a lot of time removing and reinstalling the carb after each adjusment.
I drew an illustration of how that effects the idle mix, along with a photo of measuring with drill bits in this post. Some other posts there about too rich issues too.