It's almost like it needs a 'sky hook' (sorry old Navy term for a mystery place to attach things). Really there is an odd length of angle iron of sorts that runs across and above the radio to mount it to. I'll try and find some pics of how I did mine. I may have to just email these pics as I'm just starting a new photo hosting site, not going well.
Jim


It's easier to get forgiveness than permission!
1946 1/2-Ton Chevy
1953 Chevy 3/4-ton Factory Stakebed