wire harnesses

Has anyone built thier own? I'm not wanting to spend thousands of dollars on buying one from a company that reproduces them.
How hard is it, and does anyone have a link to a site that has a schematic that i can use to build one of my own?

I have the factory 1965 Manual with wiring diagrams if you need anything for you car from that let me know so I can scan it and post for you.
Guy