1996 Grand Marquis
Single run of 1/0
21 feet from battery under the hood, passenger side, threw the firewall about 12-16" under glovebox, hidden all the way back, just had 21ft to be safe.(battery and ground on amp)
Big 3
Used 11 ft. to be safe and was more than enough, and yes I like this thread, to give a estimate of what someone might need if their going to wire some stuff up.