Where to find an engine wire harness?

You'll more than likly have to fab your own. If there's a Heavy Truck (Mack, Peterbilt etc..) Dealer in your town, you can buy a 8 in one trailer wire. It's sold by the foot and make your own connectors (ends) It's very heavy duty, I made the wiring harness for my '65 out of it.

I've searched SkiDIM, but can't find one that would work on my 74 Mustang.

My brother runs a production line at a company that makes wire harnesses for helicopters, airplanes, etc. He's going to make me a new wire harness, and use their wire printer to print whatever I want on the wires. I'm going to have him label each wire for me.

I'm pretty sure I still have the old style alternator, and I'll probably upgrade before next summer. But the wire harness I need is from the 8 wire plug to the dash, not from the engine to the 8 wire plug. Now that I think of it, though, maybe I'll have my brother make the other end as well. Or maybe I'll buy it from DIM.

Okay, so I'll use #8 for the feed/gnd wires. What about the senders etc? Is #14 good enough?

#14 wire is plenty big for the senders. They dont draw hardly any current and proper wire size for fusing correctly is not a issue here where a direct short will cause no harm to the wire(but might damage the gauge). I perfer #14 because the 16-14 awg heatshrink terminals fit well and are not huge. #12 wire uses the next larger size terminals. Also, make sure there is a breaker or fuse on the + feed line from the engine to the dash!!!