I'll put my 2 cents in...........
Just about any radio you purchase today is a "din" mount (rectangular cage). All din mounts are the same dimension, the only difference in din cages are the depth of the tabs that are bent over to hold the cage into the dash and how the radio actually snaps into the cage. Most dins have a variety of tabs cut at angles to be pretty much universal in ability to mount them.
To mount a din cage, slide it thru the opening and bend at least four tabs over to put pressure on the back of the opening that you have slid the din cage into. (Does that make sense?) Also make sure you support the back of the radio with some type of bracket so the pressure of a radio hanging in the opening does not crack the plastic on the back of the dash that the tabs are pressed against. It's a very easy project and you should have no problems installing just about any brand of radio. I recommend to stay away from the cheap/unknown brands. Any Pioneer, Sony, Blaupunkt, Kenwood, Alpine, Panasonic, Sanyo or even Jensen thats not a shaft radio will work just fine. (Most of em don't even make a shaft radio anymore). Look for din/iso mounting.
Good luck,
Don