The trouble with the old tractors is getting parts. My old Ford 4000 workhorse had a fuel pump go. Couldn’t find one at any price. Some people listed them and what they would cost but when it came time to order, it was always, ‘out of stock.’
Another big big problem with the old ones is metal fatigue. The seats give way and you suddenly find yourself under the tractor and about to be run over by what it is you are running... bush hog, sickle bar, etc.
Leading cause of death, I have heard. If you have an oldie, replace the seat and hang the old one on the barn wall.
Never had a problem getting parts for Ford Tractors.
Water pumps for example, I would go to NAPA, as long as I had the part number, and get them there.
And Ford tractors were great for water pump problems.
Select-o-speed parts might be a problem.