If it really is the vac advance:
Just disconnect it!
If U run a fast mechanical curve (say 10 initial, 34-36 total all in by 2500-2800) U can run with NO vac and do pretty good.
U will lose a couple MPG, and be a tad sluggish at cold part throttle but it will get U to your meet and back just fine.
That's a pretty quick curve for regular pump gas but a good compromise if running w/no vacuum.
What is your timing curve now, with vac disconnected?
