I have a 1954 Chevy 6100 with a 235 Straight 6. I am having to convert from 6 to 12 volt. I was figuring I would need just a standard 10si 63 amp alternator. Is there a way to calculate this. The truck is fully stock. It has a radio (currently doesn't work), a heater, lights of course, adding a trailer brake controller and maybe, just maybe in the future I might add A/C. Would 63 amps be sufficient?