Well, except for the speedo and tach (which are still quesitonable,) they don't accurately measure anyway, so whatever position you put them in is probably ok.. however, the best thing to do would be use the HEC diganostics, and then set the needles in position based on the reading of the display.. if you do it with the ignition off, you'll never set them correctly.
I think he means that if you push in the knob that changes you mileage and tip mileage, on the gauges, hold it in after or when starting the car, then you can scroll thru some things like RPM's and other crap. It's probably listed somewhere on bullitarchives or in MW. I did it once but don't remember exactly how to do it. It's too bad you had to take off your gauges to put on your overlay. I was able to do it without removing them.
Good luck with that. And I miss da burgh but more stang weather down here. Go to the O in oakland and eat some greasy food for me will ya.