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.htmlTheres a tech article by a guy that put one in his truck here:
http://alanhorvath.com/54chevy/ezwire_day1.phpThis article is agreat step by step and actually gave me teh nerve to do this myself....
Hope that helps.