Diesel engine winch from New Zealand

Are you able to supply the gas engine with belt drive gearbox only.  We want to attach a windlass rope gypsy to the gearbox so we can retrieve rope.  We need the equipment to pull 3000 kg’s.  we also need slower speeds than you advertise.  Can you supply this unit with slower speeds by changing the pully sizes.  We will need the key shaft out of the gearbox to attach the rope gypsy as in my attached picture.