Painless wiring makes harnesses and stuff more aimed at the custom car market but they sell their wire separately too. Lots of colors and with black and white tracers too on the smaller gauges. Prices are pretty high IMO but if you need lots of colors it might be a good option.
There was a guy on here a while back selling wire in sets of several colors. Anybody know if he's still hanging around and in business? Or if there's somebody else around here offering similar packages? I need to start planning the loom for the 378. Thanx.