I'm not sure, I'd have to research it. Fiberglass can be a ***** to work with at times. I basically had to build the corners of the pan from scratch with the fiberglass, the F150 ends really weren't much good. It takes a lot of time to build up fiberglass (when you don't have a structure to build off of), get the right contours, and then sand till your hand falls off so it's smooth.
If you're good with metal fabrication, that'd be the way to go. Going this route also allows you to mold it into the body, making things look that much better.