Gary,
Go to the music store, look on the back of the CD of "Shaft" and see who is the music publisher through either BMI or ASCAP. They will help you find the record publisher, who represets the song writers. Then find out who did the recording version for "Shaft". (like Universal Music, etc.)
I doubt if you can get them to license your film to use the music from shaft, as that is normally a purchasing agreement allowing all rights for film use, and not normally shared by more than one film. BUT, you never know till you ask.
Good luck.
