As a recent frequent purchaser of 7" records for my jukebox, particularly Motown, I'm often frustrated with eBay listings where the vendor lists "everything" except what's on the "B" side.
With re-issues over the years there are often many different combinations.
I've found this site which has a pretty comprehensive list by catalogue number, of every record produced by Tamla Motown, with all the "B" sides included. It runs to six pages.
Apologies if this has been linked before.
http://www.broadwayboogaloo.co.uk/singles.htm
Edit. The page up arrows don't always work, so try this page instead.
http://www.broadwayboogaloo.co.uk/boogooA56.htm