The knobs of the radio will come through the dash, there will be two nuts and the radio knobs on the front. The back of mine has a 3/4" wide strap with holes drilled into it that mounts the back of the radio under the dash.


http://s971.photobucket.com/albums/ae197/jon63c10
1963 c-10 shortbed stepside 427 BBC T16 HD 3 speed
1963 c-10 shortbed fleetside 348 "w" 1st gen big block & powerglide