lights?

[ChevLoRay]

Yep, sounds like you have a bad ground. The reason it comes on when you turn the headlights on, is because the turn signal light is reading a ground, thru the headlight bulb. So, here's one thing to check: The turn signal/park light housings probably have rust or other corrosion between the housing and the socket for the bulb. Another (easier to fix) problem is the failure of the bulb to make proper contact within the socket. NAPA has a tool designed to clean out the corrosion/rust, in a light bulb socket (with power off).

Check the wiring, to be sure the grounds are connected, and that they are "clean", i.e., not rusty or so forth. The wiring harness for the lights has all of the lighting connectors attached. Check all connections for proper make-up (male to female).

As for the side marker lights, believe it or not, they were just reflectors, when new. New wiring harnesses have the pigtails for the side markers, if you want to make them operable. I bought a new harness from www.wiringharness.com, which is M&H Electrical Fabricators, in California. Check them out, if you are interested in new harnesses.

My guess is that you will probably need new housings, because the corrosion between the socket and the housing will be very difficult to overcome....unless you can bridge them. Maybe a small sheet metal screw will tie the two parts, electrically. It's a long shot, but it might work.