Paul, I have had several do that. The radio surround I sold to Sandman had been repaired. I took the foam rubber out of it where it was separated. I used a piece of wood to provide a flat surface to exert even pressure on the vinyl outer covering.
I purchased a tube of Flex Seal and squirted it in between the hard plastic and outer vinyl covering, placed the piece of wood on the vinyl covering and clamped it down with a bar clamp and a couple of small C clamps until it cured.
Without something like the piece of wood, you will get dimples in the finish where the clamps were tightened. I did the same to my radio surround and gauge in my 87.
Edit: If you plan to remove the metal mounting bracket from the gauge pod, use a pair of pliers to hold the plastic posts that the screws go into. The screws are usually bonded very well and they will break the posts before coming loose. Holding the posts with pliers will allow you to break the bond of the screw without breaking the hard plastic skeleton.
