The wrong way to tune an engine is find out where it pings, back down timing and let the initial timing fall wherever it may... classic MP manual nonsense.

At least get two pieces of the puzzle correct at a minimum, initial and total. Initial is MORE important than total to overall driving performance. Adding in vacuum is a bonus on street cars for sure.

As a side note, vacuum advance shouldn't do anything on a full throttle dyno run. If it does, something is wrong.

Stock 340 and 440 like in the 14-18 range for initial timing. Start adding in larger camshafts and that number increases.