Success! I started writing an answer along the lines of 'can't find one anywhere' when I stumbled across this site
http://members.chello.se/seabear/detroit1.htm which lists all the singles on the various labels (Tamla, Motown, Gordy, Soul, Rare Earth etc etc). It's not laid out particularly clearly, but persevere and you'll find everything from Marv Johnson's
Come To Me (Tamla 101, released Jan 59) and the Miracles'
Bad Girl (Motown 1, released Sep 59) onwards.
"Tamla Motown - the complete Britsh singles listing" is the title of this page:
http://www.boo-ga-loo.demon.co.uk/boogoo56.htm but it starts with The Supremes'
Stop! In The Name Of Love/ I'm In Love Again (catalogue TMG 50; released March 1965).
Finally, there are complete
album discographies:
http://www.motowndiscography.com and
http://www.bsnpubs.com/motownstory.html .