I'll second what PGSigns said, I also used the American Auto wire Classic update kit for my '62. Really great kit, well made with very good instructions & diagrams. Good tech support as well should you run into any questions not covered in the instructions. I'd rewire & drive for awhile & get the feel of the truck & what modifications you may not have considered but may want to make. I know if I had been able to drive my truck before I tore it down I would have made the decision to convert to power steering during my restoration rather than doing it now after my truck is all done.
Here is a link to the complete harness kit. Good luck!
http://www.americanautowire.com/shop...66-chevy-truck