Results are what matters, if 40 works then I'll certainly re-think it.

As to the ratio I don't doubt it's changing, but not as a result of the power valves. Was there any manifold vaccum during the test? Have you visually looked at the carb at those RPM's? I had a pair of tunnel ram motors that were pulling fuel out of the accellerator pumps at high RPM. Wound up adding tiny sprngs to the check valve.

Marc,
I have tested with a vacuum gauge but it was last year.... can't find my notes. I am pretty sure the PV's are opening because when I tried 2.5 PV's (back to back test same day) the 2.5's would not open....at least at 6000 RPM and the A/F ratio had climbed to 14.1.
I agree that an internal carb leak can cause confusion, last year I had a PV gasket installed incorrectly and he took me a day to figure out why I lost idle adjustibility.
Good thought though...when I get it all dialed-in, I will confirm the PV opening RPM with both a vacuum gauge and the A/F ratio meter.
Here is some HP results same day dyno runs at KE's with just a timing change:
38 degrees
5000 RPM 589 HP
6800 RPM 753 HP

40 degrees
5000 RPM 595 HP
6800 RPM 760 HP

I have played with msd light springs and ended up with them bouncing around at idle and cause erratic idle...I don't think with your compression running it locked would cause any problems, I am noe running a mallory unilite, and it has a great advance adj you can change from lock to 20 in a minute, so far I like it...Rob

on your power valves, holley says ck idle vacume in gear, even boat, divide that # to get the correct PV, Rob

ez,
The plan is to lock-out the MSD distributor and see what issues if any arise...40 degrees is a tall number. At 700 RPM in gear, the tested vacuum is 5+ and I have already confirmed that the idle is good with the 3.5 PV. The 1400+ RPM (700 RPM spread) in neutral is the issue. Locking the distributor (permanently or temporally) hopefully will close the gap.

locking it will clean up the idle imensly as long as you have no carb issues, etc..