The other thing that often fails on the old distributors is the bearing mechanism under the vacuum advance breaker plate. The bearings and the surface get rusty, the balls stick, and the plastic cage breaks. Most people probably don't notice (I didn't) because it just stops the vacuum advance timing adjustment from working. Here's some instructions showing what's in there. The main difference would be points instead of electronics on top. https://www.atlanticz.ca/zclub/techtips/distributorrebuild/index.html If you have a good functional distributor then a Pertronix unit might be a good choice. If your distributor is gummed up, maybe look around for other options. It's all part of the game.