Looking good!
Wrt the mounting points; are the reinforcements under the rear lights, inside the trunk, still in place? I think they must be, eventhough your tail panel seems to have been replaced.
These internal brackets define the height of the bumper.
All that remains then is the width (are fiberglass bumper 1 or 2 parts?) and the 'pitch' up/down of the corners that wrap around on the sides.
Width just follows the curve of the car.
For the pitch, it is mainly a visual thing. I had to overdrill the side holes of my car slightly to get them to sit nicely. Originally they are 8,5mm holes for an m8 bolt, but I drilled the holes to 10mm so my bumper-end could be lifted ~1 mm to get a nice horizontal appearance.
If I manage (kids/holiday) I'll try to make some pics.
Erik.