1974 Plymouth Gold Duster 318 - FIND IT!

This is more than a long shot, it's complete impossibility. That long ago, anything could have happened, different state, different COUNTRY, junked, wrecked.

But even if it's still in your area, it could have been completely rebuilt WITHOUT the vinyl top, and a different color

Even with a VIN, this kind of stuff is tough

Oldmanmopar told of a car that was stolen from him, --he kept the title-- years later it came back I guess as a stripped shell? as I remember, and he didn't recognize it until he checked the VIN against the title he'd kept all those years.