from the dizzy faq
Dizzy FAQ
"The 81-87 ignition is uber reliable because the electronics are not all packed into the hot, vibrating dizzy. The finned aluminum heat sink seems to be of benefit also. Toyota moved the Ignitor to the inner fender from the head to help keep heat and vibration down."
But they didn't ground to the block again until the 100 series added a wire to block and firewall.
Sorry if you don't believe, but cleaning the hold down cage and running the ground wire works fab, and is simple and easy to try.
Seems to be up there with EGR clogs, and charcoal cannister probs, that "just happen", without altering anything else in the engine bay.
There are simple starter contact kits, even from the "HELP" series will work, but contact pitting and failure will usually cause some chatter before failure.