wiring harnesses

I have a 71 duster w/ a 360-3 spd manual-8 3/4 and I need a harness. Complete or eng bay only. Where can I find one? All the wires have cracked insulation and the harness that connects to the firewall has melted wires. I just rebuilt the 360 from the ground up and I can't get it to stay running. It has the big 3 but the only thing running it is the starter. Turn key and it goes, but does'nt want to idle. I got a new ecu and it is a 4 pin. The old one was a 5 and I tried to wire up the car with a 4 pin, single ballast as apposed to a 5 pin, dual ballast. Please help anyway you can.
THANKS