years ago they made fiberglass filler for tail lights all you have to do it is take a steel filler make it fit right then cover masking tap over the whole steal filler piece that will allow the fiberglass not to stick and then cut a pice of fiberglass cloth resin the material and once hardens then lay more and more cloth on until the desiiered thickness of fiberglass then you can model the fiberglass filler piece into the opening for the tail light when installing them on the truck you can use this SP10 second (the best of both) 2 oz. Not to thick, Not to Thin Speed Instant Activator 2 oz. Shoots a fine mist it a instant bond cause the glue is put on the area need to be and then you spray the activator and it crystalizes less than a few seconds to bond to wood metal and fiber glass you can buy any of these at a local hobby store glues comes in 3 types light light - medium -heavy for the consistency about 12.00 and the activator spray in about 9.00 depending on the brand . this would allow you attach the fiberglass filler panel to your truck and the model it in with fiberglass material and bondo to finish off the mod very simple to do . this technique is used in makeing fiberglass dashboard and door panels in car audio industry wanna know more email me at
fredstinting@yahoo.com