Stock '79 AM/FM radio
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Stock '79 AM/FM radio 'installed' into unmodified '68-'72 dash bezel
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You'll notice that the slightly-smaller opening of the bumpside bezel does cover up the Ford logo along the upper window of the AM/FM radio, but the main dial readouts can be read just fine. You could always take a file to the upper portion of the window to slightly enlarge it if you wanted the Ford logo to show.
As you can see in this shot, there are just enough threads left on the shafts to use the thin hold-down nuts. If you wanted a little more thread engagement, you could always just take a file to the chrome circular bezels around the shaft holes to make it flush there.
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These pics were just to show that they WILL fit without modifying the bezel...though a tiny bit of filing around the shaft holes and along the upper edge of the bezel opening could be done to 'enhance' the installation.