I've never used the Painless harness, but everyone I know that has used EZ Wire and Painless say EZ Wire is great, but painless is the best. It just cost a little more.

 

Since I am using a Ford 2g alternator, I needed a separate harness for that. The only supplier was Ron Francis. It was expensive, but the quality was like night and day. Ron Francis is the best quality, but you'll definitely pay for it. The painless was all good. One thing is for sure....with any of the basic harnesses, you can't buy that much wire off the roll for the price of the harness. Then throw in that you get a basic schematic, the fuse block and a lot of connectors etc. all for $200.

The only thing that I thought would be a problem for most people is that the harness came without the GM 7 wire connector installed...all the parts were included. Fortunately, I have the right crimp tool for the terminal ends. They are sort of like a Molex connector with a locking clip. You crimp the terminal onto the wire, then slide the terminal into the back of the connector body...it clicks into place. Most guys would have to make an extra trip out to Radio Shack or Fry's to get the right crimp tool for 7 crimps. The Painless manual said that some people won't be using the GM style connector so they left it off in order to have the option. You could solder those on, but by that time you'd be under the dash.

I just searched around a little. There is also American Autowire, but it appears that the prices have gone up!! Classic Update Series | American Autowire

 

Speedway motors also sells a good universal harness www.speedwaymotors.com
I used EZwire 21 circuit well worth the money extra circuits will allow for added accessories.
The expensive harnesses are for electronic engine management.