Whats best way to install glass front bumper on 71 Chevelle? Are guys reusing stock bolts with nylon lock nuts? Hidden fasteners? I know it doesn’t need much due to possible over tightening and or cracking the bumper. Looking for ideas.

On my old Nova, that's what I did. I used the stock bolts and just lightly snugged them and used loctite to hold them. Worked good. I didn't use all the bracketry though, just enough to keep the bumper in place and not flop around...

I did the same on my '71 El Camino. If I remember right (been 10 years ago) I used 4 stock bolts and no brackets. It did vibrate some but not enough to damage the fiberglass bumper.

I too have a 71 Chevelle with a fiberglass front bumper.
I used stock hardware and brackets. I did take a hole saw to the brackets to lighten them up some.

Word of advice, don't get rid of the steel bumper. I'm sorry I did.