Thermoquad low vacuum readings

Yes, part of this on page 2 (and I can't blame you for not going back and rereading the whole thread!!! :)
As a refresh here, I'm trying to dial in the freshly rebuilt TQ 6518.
Motor is a 1973 9:1 (cc'd/measured) compression 340, LD340 intake, headers, iron X heads fully ported and intake/exhaust port matched, cam is a Lunati 235/243 @ .050, .526"/.546" solid lifter, 2-1/2" exhaust with Magnaflows. Ignition is MSD distr. with 6A box.