If you look again at the GMC truck link that Rich posted a couple pages back there is a diagram with the spots on the head light switch numbered. My new switch has the #7 prong (old one did not), but looking closer at the harness plug my parking light wire is crimped in with the tail light wire into the same spot. Essentially I have the mod in that GMC truck link.

I guess in order to reverse it so the parking lights turn off with the head lights I need to cut the parking light wire out and crimp it into the #7 spot, separating it from the tail lights.