In the spirit of trying to improve the Street performance of the old gal I invested in a 6V Tach (positive ground naturally) and Vacuum Gauge. These instruments provide additional insight beyond the timing light and feeler gauges. A new speedometer cable is on its way to complete the cluster (unless 6V O2 sensors exist?). 

I was surprised to learn that the vacuum is 15" at 450 rpm while in neutral. The Lincoln shop manual calls for 18"-21" @450rpm. Anyone have a similar bone-stock Y block achieving at least 18-19" idle vacuum?

My engine also draws 16.5" @ 2100 and 14-15" @2800rpm. Do these numbers sound reasonable? 

I gave the engine a once over in search of a vacuum leak with a tightening wrench, screwdriver and starter fluid but found nothing obvious.