Personally, if it were me, I'd go buy one of the smaller fire extinguishers to keep within easy access in the car, at least temporarily until you've driven the car a few months with no issues or until you feel completely safe. My '72 had an underhood fire once. Luckily, I just had it sitting idling at my house when it happened, so I was able to run get a bucket of water and put it out before it caused any damage besides just burning up one wire. If I had been on the road and something like that had happened, the whole car probably would have burned to the ground.
Anyway, I hope you fixed the problem, and I think NoLimit has a good suggestion as well, as far as improving your ground.