No matter which harness you use, you still need a lot "stuff" to get the job done. Here's some things I found out about the stuff:
Shrink tube: There is 2:1 shrink, 3:1, 3:1 shrink with adhesive and even 4:1.
I have bought the 2:1 at swaps meets but the 3:1 with adhesive is way better. I use uninsulated terminals and the 3:1 shrink with adhesive for a joint that is sealed and won't oxidize or corrode.
Terminals: ring terminals work way better than spade terminals. The spade terminals tend to splay out when tightened in a screw head.
Wire Ties: there are a lot of junk wire ties these days. HF stuff has not strength and becomes brittle and breaks bvery quickly. I got mine from Delcity 9Link below). They are American made and worked great. I used 400, 4" ties and 100 6".
The corragated wire loom comes in different qualities. I had some swap meet stuff that lasted less than 1 year on my Elco that only saw 800 miles and was garaged 9turned to powder). On the other hand, I have some 25 year old OEM stuff that is still in great shape. How do you tell the difference? Don't know, so I don't use it - it's ugly anyhow. I like the asphalt impregnated cloth stuff - It looks more period anyway. Or there is some woven nylon stuff that works like Chinese handcuffs that I like. The best stuff is the split woven loom that Painless sells. It's pricey, but looks good and works well.
Wire: Make sure the harness you get uses crosslinked, not PVC or hook-up wire. GXL is pretty normal (General cross link). SXL has very thick insulation and is most expensive to buy. TXL is the thinnest insulation. Almost all the harnesses use XL wire but check to see.
I googled auto wire and everything else I could think of. I ended up using these guys and was satified with their price, quality and delivery.
http://http://www.delcity.net/