The last part of 3 of the Marvin Gaye's Detroit era albums 1961 to 1972, these are the duets; are now up on flickr.com
Thinking of doing the Supremes next, but maybe the 4 Tops as there are less albums.
Cut and paste the links,as there are too many link from here.

MARVIN GAYE & MARY WELLS, "TOGETHER"
front cover
https://www.flickr.com/photos/a_tom/15888544691/
https://www.flickr.com/photos/a_tom/...n/photostream/
rear cover
https://www.flickr.com/photos/a_tom/...n/photostream/
LP side 1
https://www.flickr.com/photos/a_tom/...n/photostream/
LP side 2
https://www.flickr.com/photos/a_tom/...n/photostream/

MARVIN GAYE & KIM WESTON, "IT TAKES TWO"
front cover
https://www.flickr.com/photos/a_tom/15703275260/ in/photostream/
https://www.flickr.com/photos/a_tom/...n/photostream/
rear cover
https://www.flickr.com/photos/a_tom/...n/photostream/
LP side 1
https://www.flickr.com/photos/a_tom/...n/photostream/
LP side 2
https://www.flickr.com/photos/a_tom/...n/photostream/


MARVIN GAYE & TAMMI TERRELL, "UNITED"
front cover
https://www.flickr.com/photos/a_tom/15890614585/ in/photostream/
rear cover
https://www.flickr.com/photos/a_tom/...n/photostream/
LP side 1
https://www.flickr.com/photos/a_tom/...n/photostream/
https://www.flickr.com/photos/a_tom/...n/photostream/
LP side 2
https://www.flickr.com/photos/a_tom/...n/photostream/
https://www.flickr.com/photos/a_tom/...n/photostream/


MARVIN GAYE & TAMMI TERRELL, "YOU'RE ALL I NEED"
front cover
https://www.flickr.com/photos/a_tom/...n/photostream/
rear cover
https://www.flickr.com/photos/a_tom/...n/photostream/
LP side 1
https://www.flickr.com/photos/a_tom/...n/photostream/
https://www.flickr.com/photos/a_tom/...n/photostream/
LP side 2
https://www.flickr.com/photos/a_tom/...n/photostream/
https://www.flickr.com/photos/a_tom/...n/photostream/


MARVIN GAYE & TAMMI TERRELL, "EASY"
front cover
https://www.flickr.com/photos/a_tom/15864959376/
rear cover
https://www.flickr.com/photos/a_tom/...n/photostream/
LP side 1
https://www.flickr.com/photos/a_tom/...n/photostream/
LP side 2
https://www.flickr.com/photos/a_tom/...n/photostream/