I've been pricing out fiberglass bumpers for my '73 Duster and noticed that some manufacturers sell fiberglass bumper brackets along with the bumpers. What do these brackets do other than save weight? (as in do they place the bumper in the factory location without having to use use the heavy "secondary" bumper?) I also noticed (in the pictures) that the bumpers nor the brackets have any holes drilled in them. Would I have to locate and drill my own holes in a set of glass bumpers and brackets?

If you guys happen to have some pics of the bumpers and brackets out of the box, I would much appreciate being able to see them.