If you buy wire, may I suggest using tinned? The wire looks silver rather than copper. Each strand has a tin coating. This really helps to cut down on corrosion problems. Digikey (digikey.com) has a great selection of wire and connectors. Their end users tend to be electronic types, but their stuff works just a well or better on automotive applications.
I do agree though, a purchased wiring harness will save a lot of time and grief.
David
