What kind of tools do you have? welder, oxy acetlene torch grinder, drill press for metal and skills to use them? If rebuilding is doable then look for a grey market rice tiller that needs tines, usually can get them for scrap price. Try to find one wide enough to cover tractor tire tracks. I've rebuilt the grey market rice tillers by putting a new pipe (2-1/2" sch 40 or 80) with 3/8" plate flanges and had to build complete 3pt mounts also had buy a new
PTO shaft with slip clutch. It was a lot of work (time) and I put some money into it for some steel and parts but it was a real solid tiller when I was finished and uses KingKutter tines. Just a option if you have all that's required for the project. bjr