No, they won't flash with your turn signals if you hook 'em into the park lamp circuit. Two different circuits involved there. Just hook the power to energize the relay to the parking lamp circuit and then use the N.O. relay contacts to switch power from the AUX post to the LEDS. Put a switch in that line between the LEDS and the relay and you'll have an "off override" that will keep them off no matter what.
Where might I find the park lamp circuit? - I take it it involves more than just hooking onto one of the bulb's wires then.
What are the N.O. contacts on the relay? - I'm gonna have to get my relay and look at it so I get this all straight.
Which wire goes to the off override switch: power or ground?
Oh, and I forgot to mention he should put a fuse between the relay and the AUX connection, just in case. 2.5 amp would be plenty, but they can be hard to find, so maybe a 5 amp (more common).
I already have a fuse to put in line, but I'm glad you said where to put it.
I realize I'm asking a lot of questions, but that's why I'm here and I don't want to screw this up and burn my truck down.
EDIT:
here is what my relay says (the cardboard backing)
30 - terminal for lights
85 - terminal for relay ground wire
86 - terminal for switch -- I'm assuming this is the wire from the park light circuit?
87 - terminal for power source
So if I'm reading this correct, I need to run a wire from 30 to the LEDs, 85 to a ground, 86 from the park light circuit (where ever that may be), and 87 to an inline fuse then to the AUX post on my fuse box.
Where does the swich in the cab fit into this mix?