Fiberglass Tub Help

[bohmerjr]

I own 2 CJ5 's. The first is a '74, the second is a '75. I bought the '75 for the tub since the steel factory tub on the 1st was swiss cheese. After getting a closer look at it, the '75 ( with fiberglass tub ) was in way better shape all around so I decided to get it on the road and do a ground-up on the '74 later. Anyhow, the previous owner had put a 3" body lift in. At some point, the wood blocking "sandwiched" in the fiberglass (at the mount points ) rotted and the fiberglass collapsed.Not catastrophic, but needed repair nonetheless. I cut out the areas that needed new wood and repaired with new fiberglass. In doing this, I began to question the original construction,There seems to be two layers of fiberglass ( topside and underside ) that aren't connected any more. I can pull them apart a little. I'm thinking that there was some sort of plywood sandwiched in the whole floor ( front and back ). The only thing is , there is no evidence that there was ever any wood there. I would think that even had there been wood and it rotted, I would see the remains of the plywood like I did with the thicker pieces at the mount points. So now to my questions, what should I be looking for the determine the manufacturer of the tub? How can I be certain of the original construction?