Are you talking about modifying a pto driven bush hog for a tractor to work on a ssqa with a hydraulic motor conversion? I think it's been done over on the tractor forum; the biggest factors are sizing the motor to match the pto power and speed. Also, you need a bypass circuit so the rotating mass won't tear up something when you shut the aux hydraulics off.
A lot of stuff requires high flow, you might start with the Bobcat site and see what they have for the 743 and go from there. Chances are that if a 743 can drive it, Bobcat has already marketed a version of it.