There are lots of companies that make harnesses, but personally I like stock replacement harnesses that match the wire diagram and Ford specs. You can get those from National Parts Depot, and the company is Metal Alloy. Call NPD and tell them what model you have and they will know which harnesses you need- with or without a tach, hood turn signals, etc.
Its a good idea to replace the wire forward of the firewall, because it ages with heat and the elements, however for the stuff inside the car you can get it refurbished by Randy at http://midlifeharness.com