Without looking at one pulled out, and placing it side by side with the stock Regal radio, its hard to tell.
The wiring is just a matter of input and output. If your dad used an adapting harness to wire his new deck, then you would have to find a donor car for the plugs to go into the unit. Then you would have to get a service manual, or manual of some sort to figure out what wires do what functions. Thats just to get it running.
The mounting is a whole 'nother can of worms. The radio was designed to fit certain openings. Its not a standard radio case that you can get an aftermarket kit for. You would have to make your own mounting setup to adapt it to the Regal mounting points, (or hack the car up for new mounts), and figure out how to cover it up so that it looks like it fits there.
You would be much better off getting something else. The radio might be free, but the cost and time to get it to adapt is the big cost.
Its kinda like saying you can put any motor into any car. Its just a matter of time, money, and fabrication skills.
