The one on the back bumper is screwed and bolted to the bumper. The moldings on the rocker panels are screwed from the bottom and they slide down on brackets that are riveted into the rocker panels. These brackets are about 4" or so long and have two rivets in each. There are 4 or 5 per side. I can go count the holes in my rocker panels if you want. I'm not sure how the front bumper is attached because they were already gone on my car, but I imagine they are screwed/bolted to the bottom side of the bumper.
I believe certain early year ls1 z28's had all the moldings, or else someone put way more effort than i would bother with to put these things on.... P.S. any one want to buy any side/rear moldings?? haha
Taking them off was way worth it though. The ground effects and being lowered 2" made it pretty difficult to get the lift arms under it.