this site says it has a midi file which might help you ... I have NOT D/L or heard the file ...
http://electrofresh.com/midi-8818-download-buck_owens-the_keys_in_the_mailbox.html
also here #37
http://www.dhyan.it/ricmidi/searchm.asp?dir=1
hope it helps ...
also google the title and 'chords and lyrics' and you can get the chords ...