Haven't used the grille shell but I have been running fiberglass fenders, front and rear, along with fiberglass running boards on my 37 since 1999 without any problems at all. I do drive my truck and take it on some nice trips.

On fiberglass parts I've gotten there is usually some sort of indention, or way to tell, where the bolt holes go. This usually helps get the piece in the right place before drilling all the holes in the fiberglass. I've used R&R fiberglass in Tenn for most all my projects.
Tiny makes some good points and I'd like to add to them that when you get a fiberglass piece it may still be "green" and subject to warping ect, so if not installing right away be careful how you lay it down or hang it up so it won't deform.


1937 Chevy Pickup
In the Gallery
1952 Chevy Panel
In the Gallery
More photos
1950 Chevy Coupe
Pictures!

I'd rather walk and carry a Chevy hub cap than ride in a Ferd.
I can explain it to you, but I can't understand it for you smile