I think it's possible the radio is for a GMC,due partly to not fitting the radio hole and partly due to the lettering being upside down.Radio units like the one for my '54 GMC have the tuner on the left and the volume control on the right,backwards from what is typical. Thus,trying to install it with the volume control to the left would make it upside down,and it wouldn't fit the hole.
Speed

1954 GMC 350
1957 GMC 1/2 ton
1962 Chevy C-30
1952 Chevy 6400 dump bed project truck
'98 Harley FLSTC
'66 Pontiac Catalina
'76 Chevy 1 ton Duallie
'84 Bronco II
'78 Dodge W-200
'81 Toyota 4X4 truck