I have often suggested the crank sensor and the ignition module
www.avigex.ca/xport/d1977a.jpg at that age, are just waiting to let you go in the middle of nowhere and have suggested to have one as a spare ...better yet, change the crank sensor and ignition module to be sure and keep the other as a spare....just in case.
Each is around 69$ new on ebay and changing the ignition module is a 5 minute affair ..but you must rent a puller and come with a lot of patience to extract the engine balancer for the crank sensor...and just removing the balancer bolt needs a hefty impact socket and torque bar....a nice shot from a fellow forum member is to brace the torque bar steady somewhere with the socket in place on the center bolt.....and then kick the starter for half a second.....