Hi im re building a 85 trans am and putting in a 1975 383 stroker. The car has been touched so many times it looks like, electrical tape everywhere lol. Im thinking about just rewiring everything for the engine and heater fan. I would like to run new wires right at the firewall plug. What im not sure is gauges of wire i need for what. Or is there a wiring harness i could buy? Any help is appreciated thanks!