I am ready to rewire my '68 El Camino. The car is very basic, with most accessories stripped out. There is no radio, heater, AC, wipers, etc. Should I just use the universal 12-circuit harness? Do the universal harnesses still come with a way to deal with the hole in the firwall after removing the stock harness? I just want to make sure I make a good choice now, so I don't suffer later. Thanks