318 running like a dead goat

"but there is no difference in timing with the vacuum line hooked up or taken off."

You need to solve this issue first. If the vacuum advance diaphram is torn it could be causing a vacuum leak. I would either replace the vacuum advance can or replace the entire distributor with a known good distributor. You are having to dial in a bunch of initial advance to make up for the missing vacuum advance. Check your vacuum source and make sure it isn't a ported vacuum source.