For rear wheel drive hub motor conversion kits, get yourself a fresh new freewheel/gearset that screws right onto the threaded hub from the Dillenger Premium Off Road kit.
Single Speed, 6 Speed, 7 Speed, 8 Speed, 9 Speed Freewheel sprockets. 6 and 7 are Shimano, single, 8 and 9 speeds are a generic brand that we prefer for this application.