depends... the 140 was available in 3 or 4 bottom, and i believe 16" or 18" bottoms. my experience is with a 4X16 and that is a good load for a 986. when pulling a clodbuster, we used a green 4630 and that was also a pretty good match. both cases plowing around 5 mph.
(for bystanders: the 140 is a rollover plow)
around these parts an 806 was considered a 4-plow tractor and a 706, a 3-plow tractor
so... if your soils are anything like here, you"re good to go with a 3 bottom; if it"s a 4, you can probably do it, just slower, maybe not as deep. either way, put all the weight you can on the front end. with 1200# on the 986, it"s still easy for the front to come up on ya