Vacuum advance partnr and where to find?

Hi all!

I'm looking for
a new vacuum advance unit to replace my broken one in my Dart, the engine in the car is a LA318 and it's a mechanical distributor with a single breaker point, what I need to know is what is the partnr for the vacuum advance and where can I find one?

Oh, and by the way, I've replaced the rotor, breaker point, bushings in the distributor and the distributor cap, is there something more I could/should replace while I'm at it? =)

Which year on the engine? What year on the distributor? Let me know if your interested in a Prestolite daul point set up.