Yes...Flat or slightly rounded (like modified carriage bolts) bolts and nuts would secure the plate at the bottom. In an ideal world we would have something at the top to attach to but we don't in this case, so a cantilevered rod might be a good and easy alternative. It depends on how it all fits/sits (the angle of the part of the dash where the knob holes are might cause the speaker plate to lean forward or be straight). From what I can see in all these images, it might lean about 5 or 6 degrees. Since I don't have one of these trucks to look at I'll have to depend on others for guidance. Steel or aluminum would be further down on my list of choices. Either will cost more to purchase and both will be more difficult and costly to work (cutting holes, bending, etc).
As for the two carriage type bolts, there are a couple of possibilities. The fiberglass cover plate can be recessed to fit over them or they can be cast into the fiberglass when the cover plate is made. The more I've thought about it, the more I lean toward recessing cuts in the cover plate and securing that plate and the radio with toggle anchors. What I mean to say there is the cover plate and the radio would sit independently of the speaker plate.
There is a handy channel at the bottom where the plate could sit but it will have to have something to prevent sideways motion (the two nuts in the volume/tuning holes). Also my experience has been anything on these trucks that isn't anchored will rattle, squeak, etc.
In the image below you can see what I'm thinking...the vertical line being the speaker plate, the bolt and nut at the bottom and a leaning (sloped) support rod coming up from the other edge of the dash channel there. It might be a U shape since that channel would run straight all the way across. If any sort of bolt or securing device extended out of the speaker grille part of the dash it would make this an easy slam dunk but there is just nothing there. The other image sort of shows the fiberglass cover plate with the radio oval in it.
~ Jon 1952 1/2 ton with 1959 235 | T5 with 3.07 rear end
