They don’t make TC New Englanders any more, and they never made that many left handed ones. If the stock isn’t broken or cracked, you could possibly make this a functioning gun again.
First off, make sure there is not a charge in the bore. Then gently separate the metal from wood.
As others have suggested, then time for a general cleaning. I like EvapoRust for cleaning up the rusted steel. For the stock, I would use something like KrudKutter. It will remove all the nasty stuff and most if not all of any of the original finish.
Next, I would let it dry for a couple of days, then reassemble everything, using new screws if necessary, then step back and see what I had. Any major components missing or damaged? Does the lock work (EvapoRust will remove the surface rust and finish, but lock disassembly and TLC maintenance will be required)?
Now it will be decision time. Can the barrel be saved with a rebore to a larger caliber or a relining to keep the current caliber? A $150 to $200+ investment. If the lock doesn’t have any life left in it, a replacement will likely be about $150. Still have to clean up exterior metal surfaces for finishing, maybe rust bluing if you plan on shooting the gun, possibly cold blue if a wall hanger. Then there is the stock to contend with…..
It’s up to you if it’s worth the time, money and effort. In memory of your dad, possibly. To fix up to sell,
@bubba.50 has a good idea. Or if you have a garden, tomato stakes are handy to have around.
Good luck.