You will most likely need an overrunning clutch (ORC) as well. With a rotary cutter, the momentum of the blades turning can push the tractor when you put in the clutch, unless you have a live pto or an independent pto. I know the PTO in the Ford 8N etc. was transmission driven, suspect the Ferguson to be very similar. An ORC should be available through a dealer, at Tractor Supply or similar stores, or online.
IIRC, that size tractor works best with 5' rotary cutters. Good luck with your new tractor!