Welcome to OCC.....
The PTO Belt is :
954-3006, Belt, Mule Drive (982 only).
As for the slow reverse, I would suspect the Relief Valve(s). The Reverse is the RH Valve. Pull it out and check to see if there is "gunk" in it or worn "O" rings.
You could also swap valves around to see if the problem followed the swap.
Check it out and report back.