They are very rugged tractors and parts certainly ARE available. Gas engine parts not as common as diesel, but still can be found. Many parts that Case-IH sells over the counter are made by Mahindra Company. B-414 was built 1961 to 1966 and is an upgraded B-275. The B-414 was also still built new up to a few years ago with a few upgrades and sold under the Mahindra name. Same basic tractor with modern sheetmetal and a few refinements. One model was the Mahindra E40-DI which is basically a B-414 with a direct-injection engine stuck into it and most else the same.
B-414 gas engine is the BC-144. Also used in the B-275, 354, 364, 434,,3414, and 3444.
B-414 diesel is the BD154 and was used in even more IH tractor models.
In regard to the BC-144 gas engine, it takes the same sleeves as the BD-144 diesels and they sell them on this website. Engine gaskets are availablew aftermarket of direct from Case-IH.
Only oddities on the engine are two things. #1 the distributor. It's a British Lucas and same as used on some MG and Mini-Cooper cars. Parts are not a problem, you just have to know where to look. #2 is the carburetor. It is a British Zenith and has nothing to do with the USA Zenith carb company. Same carb is used on many small British cars. I just bought one brand new for $150. Original is a British Zenith 30 mm model VN or VNN. One has an accelerator pump for easier cold-weather starting, and one does not. I'll add that there are many other 30 mm downdraft one-barrel carbs that fit; no big deal. Also, they sell repair kits for the VN or VNN carbs right here on this Website. From what I've experienced, these tractors are usually great bargains. Live PTO, live hydraulics, differential lock, hi-low range transmission, etc. I've got several and love them. About the claim of no parts? I just rebuilt my neighbor's IH 354 with the same BC-144 engine as the B414. Bought a complete engine kit with all main and rod bearings, gaskets, pistons, rings, sleeves, etc. for $550.