If you have to make a splice in a circuit, strip and solder the splice and cover it with heat shrink. Finally, I marked each circuit with numbered tabs, then wrote down which color and number goes where.
No one will mistake the end product for something out of a Winston Cup car. It is simple, effective, and clean. And if it looks better than what you have in your race car now, it may be a good way to spend an off-season afternoon and eliminate electrical failures.