In later years, well after the "N" series was history, Ford did offer a couple models with engines that were diesels by design that were converted to gassers. (3-cyl in 3000/3-cyl. in 4000) By starting life as a diesel, they had cranks,rods, ect that were heavy duty enough to survive the power and vibration of a diesel. The most well known gas to diesel conversion I know of was the Oldsmobile V-8 to GM diesel of the late 70's/early 80's. In case you don't remember that one, it WASN'T a very successful experiment. Massey Ferguson used a Perkins 3 cyl and 4 cyl. diesel in a few late 1950's tractors, along side of 4 cylinder gassers from Continental. At some point, Perkins and Massey teamed to build a VERY successful 3 and 4 cylinder gasser with those diesels as a base to replace those Continentals. They share a LOT of common parts with the diesel cousins. They were EXTREMELY popular. MANY still prowl the fields and farms of the world.
Long story short, the Ford N series engines were capable of producing enough power for their intended uses, but they weren't "over-built" to the point where they would have been a candidate for converting to a diesel. There are conversion kits available to install a number of commercially successful small diesels in place of the little Ford N motors. I've seen Perkins, Kubotas, and even a 3 cylinder Ford installed in an N chassis. My question would be.....WHY? For LESS money in the long run, you could sell the N, buy a ready made, non-cobbled, off-the-rack diesel tractor that WASN'T an oddball conversion, that would most assuredly be less trouble, more efficient, and prove itself to be an allround better performer.
But that's why we have mountains......So someone can climb them. Gotta do what you gotta do I guess.