No no no no. You can't mount a small-face radio in an opening designed for a big face radio. It is TOO SMALL. So replacing the front of a big-face radio with a small face setup IS something you can do but it will _not_ fit in a car that has a big face opening, which your car already has. The panel has been enlarged or replaced.
If you want to go back to a small-face radio, you will need to replace that panel.
If you want to change the markings and knobs on your big face radio, you can do that too. Replacing the black plastic "Europa" name bar with one that says "Europa TR" is trivial.