There is no magic usually in our old cars, you can fix this
The hard part is figuring out exactly what is causing the system failure
I've heard of more than one professional drag racing teams swapping out all the electrical parts and wires on a race car at the track between Friday night and Saturday along with doing the same thing on Saturday evening
Your issues make me think it has a corrosion or what we use to called a swinging open issue on a connection or terminal end, ends Especially when cranking the engine over putting a bigger drain on the electrical system Good luck