OK, to add to the confusion, I just looked at the electrical specs in the forum for a 72 GT and it shows the rear yellow lights(turn signals) as the outside pair and the tail/brake lights as the inside pair. This corresponds with what tarquin is saying but against what old hippie is saying. Anyone else want to try?
However, some owners have intentionally put the red lens and brake light on the outside as a way to make the GT appear closer to the cars behind them when they hit their brakes. I seem to recall seeing a thread on that .
My silver 1:18 scale metal die-cast MiniChamps model sitting on my desk here at work has the reds inboard and the yellows outboard. It's quite accurate in detail, I'm sure they just copied what was.
I like the yellow turn signals mounted outboard. I did add an very bright LED 3rd brake light mounted outside the car in the vents above the rear window. Since the car is so low I felt higher was better for visibility. That vent is just an inch or so below roofline, can't get much higher.
Maybe we should all sign in with how our lamps are ...my reds are out, which make sense as "clearance lamps". It IS possible that the reason for the confusion is that North American GT's could be red out, while UK cars were red in... any thoughts on this?
Just checked the wiring diagrams in 3 manuals including the master 1973 Opel Workshop Manual and the are ALL Yellow outer and Red inner. This would make sense as your indicators should be the most outer lights on your rear end so as to INDICATE which direction you are intending to turn.
Oh, and here is a pic from the Opel Museum in Russelheim, note the Aero concept plus the origional yellow one in the background.
Thanks to all who replied I just wanted to have the correct position. I know the auotomakers like to move things around from one model year to the other so it looks like they actually did something new.
I've been asked about the LED style 3rd brake light, so here goes.
I got it from JC Whitney, I've seen them in local auto stores. I took the printed circuit board out and tossed the black plastic rear window mounting setup. There are about 20 red LED's and associated limiting resistors mounted on the board. I wanted lots of LED's for more visibility.
I made a very thin (like 28 AWG) black twisted wire pair using teflon wire (very tough - but very thin insulation) about 6 feet long. Soldered wires to the to the board. Trimmed width of board to a minimum with a dremel.
Installed board in vent using some 0.020" thick Ultem film to insulate solder points on back of board from metal chassis ground. Any durable plastic film will work, I've cut up 2 liter soda bottle in a pinch. Used clear RTV adhesive to glue plastic film and board assembly into vent.
I tried drilling a hole inside the car at the back of the head liner just above the rear window rubber molding to run wire...no luck. I've never had the headliner down so I didn't know how the sheet metal up there is setup. I didn't want to mess up my perfect headliner, so plan B.
Plan B. I ran the wire pair to the left inside the vent, then ran it out the very left corner of the last vent to the rubber rear window molding just below. Dressed the wire inside the rubber molding down to the bottom corner. Was able to poke the wire down through the bottom corner gap between the window glass and the sheet metal window cutout. Used a bit of RTV to assure rubber window molding was OK. Once inside car just spliced into drivers side rear brake light wiring.
Makes me feel better knowing I've got a 3rd brake light.