Painless makes a great wire harness. However, the guy that is doing my car uses OE Electrical Harnesses and Switches. You may want to talk to him to get his insight. He restores Pontiac's for a living and knows his craft very well.
He can be reached at 513-314-9806 Chris
1967 RA convertible 1968 H.O. coupe - sold 1976 Trans Am - sold 1985 Trans Am - sold