Randy, it's just sheet metal..... it can be repaired or replaced. Pounding the dents out will cause a lot of stretching, but that can be dealt with also. Or, here's another alternative.

If it were mine, I would consider leaving the outside flange, then coming in about 1" to the flat area of the pan and cutting it out. I would then make a very precise pattern with posterboard, transfer this to 20ga. and cut it out and weld it in place. Careful welding and some grinding would have you a new panel with minimal filler.

Or, make a template of the tail pan out of 3/4" plywood, then another piece of 3/4" cut 1" smaller all the way around. Sandwich a piece of 20 ga. inside these two, clamp them together and form a new panel. This is called hammerforming, and old sheetmetal working method.

No way I'd give some company that much money for a new one, then have to mod it to make it fit!!!! So loose of tolerances when these old cars were built, never yet seen a re-pop panel that fits correctly!!!