[wildturkey]

There should be a bracket where the back of the stereo ends, welded to the car, that a rubber boss (screwed to the stereo) mates with. A good stereo can should hold it with out the back mount though.

There is an aftermarket metal stamped panel available that your can slides into that gives it a 5 mm lip around the front. Like a washer of sorts.

Any car audio installer has seen them. You need to ask the installer at an audio shop, not the salesman.