Return the Painless and go with AAW. They have a Classic Update kit for your 67 which will do your entire car.
http://www.americanautowire.com/64-67chevelle.html
Good Luck...I am about to do my 72 and have been researching harness kits for months and for the price and quality, the AAW is tops.
We also might want to move this to the Electrical Forums
Jacen