Dropped in new vacuum advance this evening. Comes in at 7 inches, full advance about 10 inches. Paranoia is high, I checked phasing with new can, just in case the arm is slightly longer or some other ridiculous problem. The stamp on the arm says it pulls in 11 degrees, timing light says 15. Quick test drive, no pinging at part throttle. I'll run it for a while see how it does. Currently at 16 initial, 34 all in, two heavy springs. I should have checked when that comes in again, but I just didn't have it in me. Last time I checked with both heavy springs it was all in about 3500rpm but that was with advance plate at 12 degrees. Long term, I've found a company that will build up a nice billet distributor to spec for under $300 delivered. Once I get timing exactly correct, I'll order one up and put this timing issue to bed for my lifetime.