My vote is to do it right. You might be able to find a decent used wiring harness pretty cheap but if there are already problems you might just get a repeat performance of the meltdown. There are several members up in your area that may be able to help and some are vendors.
You can serarch in these forums for parts:
http://67-72chevytrucks.com/vboard/forumdisplay.php?f=8
http://67-72chevytrucks.com/vboard/f...play.php?f=195
Vendor list:
http://67-72chevytrucks.com/vboard/a....php?f=87&a=10