Bob--That's very similar to the configuration of the ashtray assembly in my '65 Mustang, but I since learned that my '57 has a simpler arrangement that mounts using 3 sheet metal screws--one top center and one on each of the two sides.  The screws are about 1/2" long and look very similar to the ones that secure the box in the glove compartment.  Thanks, Ron

If it is like the one I have in my truck, there should be a u shaped piece that screws into the dash and provides support for the tray to slide in and out.

I'm attempting to install the dashboard ashtray in a '57 Ford Ranch Wagon that was removed a few years ago by an unknown prior owner and came to me in a large zip-lock bag.  I only have two pieces--the inner tray that would hold the cigarette and ashes, and the door/face plate that pulls down to reveal the inner tray.  I see how these two pieces clip together to form one unit, but I don't see how the whole unit fits into the dash. There was no attaching hardware in the zip lock back, so either I'm missing some parts, or it's a compression fit in the dash.  If anyone can give me a couple pointers on how this is accomplished, it would be much appreciated!  Thanks, Ron ...