I have over 7000 miles on my fiberglass fenders. The fronts are a little thinner then the rears and are showing a few stars in the paint. The stars are from rocks, but you really have to look for them. The stars are nothing compared to the chips on the front side from bugs and rocks and what ever else has hit them, the '37 has a lot of area for impacts! I have heard that if you get them sprayed with bed liner before painting, they will hold up much better.
My rear fenders are two inch wider then stock and I really like the look. These are so strong, you could set on them with out any fear of cracking. I bet they weigh three times what the steel ones did.
I say go for the glass for now, enjoy the truck while you repair the steel, then sell to glass to the next guy in the same situation. Joe
