There is a distinct difference between 67-68 Camaro bumper mounting. What years are the brackets for? And don't go google it or look at URL's, first think about what the "evolution" of the bumper mounting may have been.
I learned this years ago when I had a Camaro and found that it had been hit and had the wrong bumper (well that I am not sure, the bumper may be the same) and brackets on it. Never knew looking at it, it was all in the mounting.