A couple of those pictures look familar
Not all gen.II camaro tachs are the same. The one I used required me to cut a 1 3/4" hole in the back of the housing. It protruded through only about 1/4" so the printed circuit fit over it no problem. I sealed the hole with some 10mil vinyl tape. To allow light to reach the face I spaced it away from the front plate using cabinet door silencing pads. These are adhesive backed, and available at any hardware store. I'm probably going to disassemble mine to repaint the needles. When I do I'll take a couple more pictures.