I went the other way, I put a big block harness in my 340 car. It was a good harness, and it had the A/C wiring, so I decided to use it. All I had to do was shorten the distributor leads, which were dried out anyway. The alternator leads were dried out too, so I just did both using the same color wire, soldered everything, and re-used the original connectors or ones that matched pretty close. It looks and works great, no problems yet.