lang,
I got a 16 gauge metal plate at Home Depot and some metal cutting jigsaw blades and a 2" metal cutting hole saw... I first cut the holes with a 2" hole saw on a drill press and then cut the plate the same size as the storage bin that I took out. I cleaned up the edges with a bench grinder and diamond stone. Since the bin I took off had a flange that interfaces to the radio, I tack welded a flange to the back upper edge of my plate. I don't think this is really necessary but it makes it a little easier to 'tune' the fit to the radio since the upper edge is held flush to the radio.
To attach the plate to the radio I made a couple of straps (~5/8" wide), prebent them and attached them to the plate at the upper edge between the 1st and second hole and 2nd and third hole. If I did it again, I would probably want to attach them to the bottom of the plate since the top is held in place by the radio. You've got to be careful at the bottom though because there is an upturned flange on the instrument panel that just barely allows you to install the gauges. You can't go any further down than the bottom of the holes so the mounting straps will have to be attached between the holes.... If necessary, I was going to file down the flange on the IP but I didn't need to.
The straps shoul be pretty close to meeting up with the bracket that held the bin on the bottom of the radio. Adjust the bracket shape and drill holes and use the screws that attached the bin to attach the gauge plate. Tweak the fit as necessary. 16 gauge is stiff enough not to move during normal use but just soft enough to be moved to fit perfectly when needed.
To finish the plate, I flattened the visible surface on the diamond stone (since I had a few bumps from welding on the back side). I then used spot putty and wet sand primer to get the surface scratch free. I finished it with Rustoleum satin black textured paint (Home Depot). I probably didn't need to get the surface completely scratch free because the textured paint covers up a lot of imperfections.
Check out the sketch of my design attached.
Hopefully this helps.