I've seen some 9 and 11 HP Briggs with 6:1 gwear reduction used on capstan winches on boats,trailers and well drilling rigs that use 400 lb hammers ,it'll work ok as long as you make sure the engine only turns the winch drum and none of the load is transfered to the PTO shaft on the gearbox..you'll probably need more reduction than just the gearbox provides,I've seen guys rig an old forward/reverse tranny from a sit down mower so they could have power in/out instead of just "in" only with free spooling for "out"..