Hope you can find the car. I can imagine the sentimental value of this car.
That was a nice looking car but that car may have been painted over with how popular other colors were over the autumn bronze color.
As Cuda Hunter stated, more info is needed.
There is a member named Devil on here that runs the site "cars in barns" or something like that. He might be able to give you some insight as to how to better hunt down this car.
It's been over 20+ years since being in your dad's possession so anything could have happened to it. Maybe, if the car doesn't show up, maybe make a tribute car to remember your dad's car? I often think of doing that for my sister's old 1981 Trans Am that got totalled after having it a few years.
Hope you find it!
Don't give up!