I just recently had similar issues with my cousin's '95 GT too. We confirmed both the battery and the alternator were good and didn't find any shorts. That's when we started looking at the ignition components and found the coil was going bad. Once the coil got hot after running for a while it would intermittently fail. After replacing the coil, the car has been running strong!
I know it's rare for the coil to fail intermittently, but it's still something you may want to check. Hope this helps!