Lean pop off idle?

Assuming it's a 80770 mdl, it has a factory installed #31 squiter. Plenty for a dual plane intake. The primary jet is #70, "might" be a little lean for your application with that size carb. And the PV is a 6.5. No reason you couldn't step that up to a 10.5 with that cam & vacuum.

As far as idle mixture settings on all the Holley's i have had, (many), turn in to stumble, back out to smooth and go 1/8th turn out. The vacuum will be what it will be.

All that said, i'm not yet convinced it's a carb problem. Something haywire in the timing could very well be it. Just hope it ignition and not cam. :)