Once you have most of your side fiberglass panels, your rear seat, trap door all out the next step is to lay it in. You may have to remove one or both of your seats. My car was bare when I put mine in. From the trunk you should be able to just barely see the spare tire mount, i just marked from the bottom with a china marker or paint pen.
Once you have that measurement, it's pretty straightforward to measure over to the shock mount holes.
as for the rivet holes, that should all be pretty obvious with the tray setting in your car.
My two cents worth.