Artifacts from shipwrecks are not left in there "as-found" state, they would fall apart.

They are stabilized, then displayed.

I have a unique idea on what should be done with car.

Clean and stabilize the body and frame, but not restore it. Maybe coat it with clear to seal the rust and prevent further decay.

Clean the interior, try to save as much as possible. Put it back together.

Rebuild the engine, trans, rearend and brakes, but leave the outsides of them as original as possible.

Then you have a running car, but it looks much like it does now.

Put in museum for all to see.