if the weld on arm end works for the implement end.. it will work for the support end. that or you can get another arm..e tc.
on the castle nt. in an emergency.. you can always make one.
i've made castle nuts for tie rod ends plety of times. just takes a vice and a say blade or die grinder / cutoff wheel to notch a nut.. etc.
I'd do that before holding up a project too long if I needed the tractor.