Any fix for radio size mismatch?

[rough69]

Hi there, long time no post

Just picked up a '71 GMC and it has what I'm assuming is a common radio size mismatch on the older shaft mounts.

The dash is uncut original 1971 but the radio is some 80's Realistic radio Shack brand and the shafts are just laying there because it is narrower than the original GMC deck and the face of the deck is a smaller rectangle than the factory opening.

Is there a plate or something I can buy aftermarket to maybe bolt to the shafts here and take up the gap everywhere?

Sorry for the bad photo