I'm pretty sure the Chevy and GMC radios of the late 50s are schematically the same, but the GMC is mechanically "upside down" from the Chevy radio. The tuning knobs and dial are at the bottom of the GMC radio and stick through the roll at the bottom of the GMC dash.
If you have any interest, I have a .PDF file of the Sams PhotoFact for the GMC radio that I could send you.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12
'52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
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