I noticed when I was working under the dash on my '71 that there is a flat mounting surface just under the radio hole, sort of to the right side of the hole as you're looking at the radio, that's maybe 3 1/2" wide, and has (2) threaded holes. The surface is horizontal, as if a component is supposed to screw into the threaded holes and hang there.
What is this mounting surface for?
What is this mounting surface for?