Mine was really rotted - 33 years of sun, moisture, and who knows what else really took their toll. The vinyl covering had pulled away from the fiberboard wells and was faded, split, and torn. The shelf itself had tears and rotted corners and edges. Unfortunately, I didn't take any photos of it in this state, but you get the idea.
First, I removed the black pebble grain vinyl from the fiberboard. It came off it brittle bits and pieces.
Using fiberglass (in some places, several layers), I rebuilt the missing corners, edges, and re-enforced the crumbling parts.

The seat belt slots were all but gone so they had to be rebuilt.

This edge is about 60% fiberglass and 40% fiberboard.

Roughed in the new corner and edge.
The front edge (that runs along the wall behind the seats) was warped and torn. I clamped a 1" x 52" x 1/8" piece of aluminum along the back edge and fiberglassed it in place.

This had to be done in stages and several thin layers of fiberglass was used.

Finished with the 'glassing, sanded and shaped with a dremel. It looks bad, but it's pretty rigid and structurally much sounder than before.
I picked up some black fabric that has a nice texture (think very very short nap carpet) and has some stretchability. Using spray adhesive, I glued it over the top and tucked it around the sides and edges.The wells were a problem area as the material wouldn't stretch enough to cover the bottom and mold to the sides too. I wound up having to add in separate pieces for the wells and using some free form gluing, cut and pasted them into place. The thickness of the material helped blend the edges but they are visible. I get really anal about things like this but I accepted it as the best I could do unless I wanted to spend the money and have them professionally covered.

Installed...


Seat belt slot. The actual hole is much bigger but I just slit the material and slipped the belts through...

I know you can buy fiberglass parcel shelves for about $200.00 but I'm not trying to make a showcar, I just want a nice driver.
Aaron
1976 TR7 FHC (an ongoing project)