We've got our fiberglass bumper blocks done. They will come with both sides the same length, so they can be trimmed to fit in various locations. I have them mounted close to the lower grille so that I can use our lights in the former bumper shock holes. If you want to mount them over those original bumper shock holes, merely trim one side to match the contour of your lower valance. They come with a black gel coat, so they can be painted or left as is. $90 a pair plus $16 shipping in the US.
I bolted mine on. If you mount them through the oem bumper shock hole, you can use a strap across the back of the hole and bolt them together. As I stated, these are not intended to absorb impacts, though they are pretty heavy construction. They are merely to comply with bumper laws once you remove the double tube bumpers