Hi kujaneckinga,
I normally hang out in the Kubota forums.
Have you seen a plow that fits a JD M? I used to have a 1 x 14" (or 16", I don't recall which) rollover plow that came with my M used. It was a strange looking site! As you can imagine, the moldboards were 180 degrees opposite, and it had the long round bar to pick up the 3rd point lift under the belly of the tractor.
I tried to use it a couple of times at my Dad's 1/2 acre garden, but I never got it to plow well at all. Maybe I didn't have it set right, I don't know. Seems the bar would slam all the way over to one side and it wouldn't turn the dirt well. I never figured out how to secure it to the other side, so the plow angles would be better.
Instead, what I used with more success was the JD spring shank cultivator/chisel plow. I put chisel plow sweeps on the shanks and it would work the heavy ground up well. Working it multiple times about a week apart gave me some great looking soil.
My tractor and plow garnered a lot of stares, but wasn't that functional.
Best wishes in your search.
Ron