If you have the means, get the American Auto Wire Abody harness. It is worth every penny.
I am a complete idiot when it comes to electrical, but the harness design and instructions make it incredibly simple. Not to mention AAW's customer service/tech support really shine.
Check out their instructions for the gauge cluster. Clearly shows you how to go the factory or aftermarket route..
http://www.americanautowire.com/PDFLink/92971259 510605 IN 0.0.pdf