For your front end sheet metal hardware I go to McMaster-Carr and buy in bulk. I can get a box of 50 or 100 for what you'll pay for 20 at the hardware store. This also gives me extras for the next project.
https://www.mcmaster.com/standard-hex-head-screwsOnce you get to their web site via that link, lookup Flanged Hex head Screws and then Medium-Strength Steel Flanged Hex Head Screws–Grade 5 and you'll see the exact style bolts Chevrolet used.
Steele Rubber will last, the other stuff comes from Taiwan/China and a few years out will start to check and crack. I have window rubber from Steele on my '35 Coupe that was installed in 1980 and it all still looks good! It's worth the extra money because you only have to do it once...
Mike B
