Cool old truck! Firstly, you must run tubes with those wheels. I would not call them split rims... though some folks do. That is a wheel with a detachable ring. All 1-piece wheels, those that can mount tubeless tires, are drop-center. The wheels on your truck are not drop center, and the ring must be removed and replaced to mount/dismount tires. That's when it can get dangerous. As others said, tire shops familiar with big trucks and ag equipment will have experience with those kind of wheels. Of course, first you have to get them off of the truck.
