All these aforsaid points are valid. I am not the expert here but I do have an electrical background but it was in construction not in solid state stuff. Healey Rick makes a good point about the radio. Back in the day if some of us youngins wanted to put in an "American" radio we would mount it so the radio metal enclosure would not touch the metal of the car. You would also have to isolate the antenna. Big Pain so I never did it to my car. But aside from the radio, let me just go thru my thoughts on the items. Oh yeh, also when I redid my car about 2 years ago, I put in an alternator and reversed the polarity. I installed two fuel pumps, bought a new one that was dual polarity, and USED MY ORIGINAL ONE THAT WAS MORE THAN 30 YEARS OLD. The original one then quit after about 100 or so miles. The reason I installed the old pump was to just see if it would work. It did, for awhile. I never reversed polarity on anything else. The wiper motor will work, the blower motor will work, the horns, the flasher, the gauges also. I did wonder about fuel gauge because of the direction of the magnetic windings thinking it would try to operate in the reverse direction, but while I was cleaning it, the windings all unwound, and I ended up rewinding it, but I put them back on the same direction that they were, and it works. But I did have to adjust it for accuracy. So I'm pretty sure the fuel gauge doesn't need to be changed either. So doing a generator flash and taking precautions about the fuel pump are the only things that I think need to be done. Dave.