I ask because I have to replace mine too- darn desert packrats. Here's what I don't understand, you can pay anywhere from $150 to nearly $700 (at LMC, see pg. 93 at http://www.lmctruck.com/icatalog/ca/full.aspx?Page=92) and honestly I can't tell the difference. Do I need a harness made specifically for my stock '57? I might, as I'm a complete noob at all this, and I've heard of troubles with leads being too long, too short, etc. I contacted Haywire and Ron Francis, and both assure me their less expensive kits will work- But in talking to some people in town they recommended going with Chevy Duty- only problem is Chevy Duty is no longer under that name- and I can't track them down. I'll start a new topic as I don't really understand the basics about what's needed in a wiring harness- so deciding who to buy from is a bit premature.
But keep this thread posted with what you find with your new harnesses, and good luck!