I just bought one of these form EZ Wire at a swapmeet for $160. I also havn't put it in yet, but it looks to be well made and has a nice fat instruction manual and adapters for various fittings etc. By far one of teh cheapest ones I found, but seems to be well made.

http://www.ezwiring.com/wiring_harness.html

Theres a tech article by a guy that put one in his truck here:

http://alanhorvath.com/54chevy/ezwire_day1.php

This article is agreat step by step and actually gave me teh nerve to do this myself....

Hope that helps.