The investment value is low. Keep it nice if you enjoy it.

I shoulda grabbed onto some nice Cutalsses and 88 convertables fifteen
years ago. I don't think a sedan will ever "take off" the way prices for
those have.

Let me add that I like those cars and recently owned a '78 Ninety-Eight
Regency. Rusted bad in the local climate, was having a lot of repairs
and finally caught fire. Son was driving it. (unhurt) Ruptured fuel
return line, I think.

At one time I wanted to keep it really nice but don't have the storage
and needed to drive it.