As far as power goes, you should use a relay. Assuming you have driving lights, not fog lights, they should only come on with the high beams. The "control" side of the relay should pick up power from one of the high beam circuits, go to one side of the relay coil and then to a dash mount switch and on to ground. This way, for the lights to come on, you must close the switch and have your high beams on. This circuit is low current and you can use light gauge wire. The high current part of the circuit runs from the battery, with an in-line fuse, to the relay and on to the lights. There should be a ground lead on the lamp or the case will be grounded. Run a good ground to the chassis. The bumber is not a good ground. Relay kits are available in most auto accessory places. BTW, if you do have fog lights, the control voltage is picked up off a low beam wire. Everything else is the same.

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'93 850GLT
'83 242TI Flathood