I'm looking forward to hearing your Motown project! There are so many fantastic songs that came out Motown. Here are a few of my votes for you to cover, as if we get to vote ;-)...
Ball of Confusion
Just My Imagination
Stop! In The Name of Love (I can hear the arrangement in my head, but there's no way I can pull it off)
Where Did Our Love Go (Another arrangement I can hear, but can't play)
My Guy
What Becomes of the Brokenhearted
On a side note, have you heard Marc Cohn's album "Listening Booth: 1970"? If not, I think you'd like the approach and arrangements he takes to some classic '70s songs. His interpretation of "Wild World" is worth the price of admission. Other highlights are "The Letter", "No Matter What", and "The Tears of a Clown".
--G