It's not hard to do. The idea, on paper at least, seems like it wouldn't work. But it does, I did it on my cadillac, and my truck, and several of my previous cars. You just cut the ground wire on the marker light (you might have to add some wire to make this reach) and clip it into the turn signal power wire for the parking lamp.
I dont know the color of the correct wires because I dont have any diagrams for these cars yet. But you can figure it out fairly easy.
The ground for the side marker light is almost always solid black. If its not and you dont know which one it is pul the bulb out and use a multimeter on each side of the connector (make sure the lights are NOT on when you do this) and test for continuity/resistance between the connector and the frame or some other metal surface, of the car.
To find the turn signal wire on the parking lamp, turn the parking lights OFF and the hazzard flashers ON. Pull the bulb out of the socket and test each connector inside it for 12V cycling on off on off. One should show 0V constant, the other should switch back and forth. You can use a test light for this as well as a multimeter. You should be able to figure out which wire goes to which connector by popping out the hold down clip on the back of the socket. Just don't go yankin the wires out.
Edit:
Just for clarification, here's a very crudely draw sketch of what the finished product should look like.
Keep in mind this will make the lights alternate flashing when the parking lamps are on. But they will flash together when the park lamps are off.