I'm sorry, but I really don't know much about the names of stuff on old
tractors. Is it a wide front end, or narrow? Is this the part the wide
front end pivots on, or is it the part teh narrow front end rotates
around to turn the tractor????

in any case, brass is a common bushing material. It is soft, and
functions well for places that are greased regularly, turn, but are not
pounded on. So brass is good for bushings for the steering wheel shaft,
but not so good for wheel bearings.

UHMW is used for bushings, but it is not as tough as brass.

Steel is used. Again, you need to grease it. Harder obviously. I'd use
mild steel. The goal is the bushing material should be the softest
material around so it wears out the fastest, instead of your shaft.