Paul,
I have my rear set up tacked on with duct tape as I decide the same. I took several photos of a coupe and used that and the photos from various picture books to make the placements. The lights are at the same level as the teardrops on either end of the location and at the same height. The reflectors are roughly half-way to the bumper between. The shine-down is located the width of my hand below the lid (right now it's a strip of wood in the same size held on with tape. There should be enough space above the light to place the Porsche and the 1600 logo. I taped a license plate beneath the light, leaving even space between the plate and the bumper. After my wife gives her critical review of the locations, I'll drill the holes. I have yet to find an actual spec for the locations, so I just did the mock-up (I used spray paint can lids to imitate the lights.) I may move the license plate up very slightly.
If you find an actual measurement, I'd like to see it, also.
John W.