According to the 400Kabillion posts I read threw to find this little bit of info:
The Legacy stock radio has a single din pocket that gets tossed when they upgrade to premium stereo system.
This info was found in a post from 2002, so My guess is there may be more available at wreckers.
I'll do some shopping around and try to locate more info.
p.s. If anyone knows of another post which some specific's, please let me know.