Your tire width is around 6'.
As rear blades are mostly used on an angle, usual recommendation is to multiply blade width X .70, which is 7' for the blade you are considering.
Perhaps a tad wide. Not bad.
Your Three Point Hitch is Category I. That blade may be Category II. So it may not fit your hitch. Check before you take it home.
Mostly for grading my one mile gravel road I live on.
Asking $975, still worth it?