I have a soft spot for 9N's. My grandfather had one growing up. I can still remember the smell of the barn he kept it in. A mix of cut grass, grease, oil and leaded exhaust fumes.
Original owner had a Farm next door. I had helped him hay with that N when I was barely old enough to lift a bale. His son got killed in Vietnam and no one to help keep up the farm, he sold it to another neighbor.
When that neighbor was selling his farm our family got it. A great deal with many original implements too. He thought engine was shot fouling plugs. But it was the oil bath air filter full of crud and some water at the bottom, it was sucking that dirty oil into the intake.
I fixed it up and I've done all the upkeep since then, ~1985 40 years. Never had to go inside the motor except adjust the valves. By the time it's down on oil it's time to change it. Still 6V + ground electrics but it starts in winter when I move snow or skid logs.
It won't do all the things a newer tractor will do, but simple to work on, unlike new stuff. Usually with just the tools that fit inside the lunchbox size toolbox.
The Ferguson I got last year is much the same. A little more powerful OHV engine and better brakes. Still fixing stuff on that.