Years ago, about the time GM's Detroit Diesel Division was developing the 60 Series, there was a proposed joint venture between Deere and GM to form a new diesel engine company to be called "Dedec". Detroit Diesel was having lots of oil control problems with the 60 Series so Deere engineers helped them with the ring package - maybe other things in the engine too. Yes, Deere 4WD tractor prototypes did have 60 Series engines in them, but when the joint venture business deal fell through, the 60 Series was replaced by Cummins shortly before production of the tractors.
Interestingly, Deere engineers also developed the direct injection head for the Onan "L" Series diesel engine. Later, Cummins bought Onan so that Deere work got labled Cummins. As I recall, there was also some unit fuel injector work of Deere's that eventually fell into the Cummins camp.
Also, Deere experimentally put V8-955, 6-619, 6-466 and 6-359 engines in many trucks all across the US and even one in Canada. Drivers liked them very well but Deere's upper management decided not to go into the over-the-road engine business largely because of product liability concerns. Later, the Deere 6-359 was strongly considered for the HUM-V.