I have two of these Echo 3900 Short blocks (SB 1018) converted. Farmers Exchange still have them listed in the Echo section fro $139.39. They are a very easy conversion, All you need to make is the ring to fit on the intake with a couple of set schews and some sealer. (epoxy) The prop hubs and mufflers can by bought from BME, made fror the 50cc Classic engines. the 40cc (3900) also has beam mounts. An hour or so of machining you should be ready to go. Also Brillelli customes have fittings to install the carbs. The engines with mufflers, carb, Hangar mounts and a rohr BME 20-8 prop No ign, weighs 3# 6.6 oz. Check my gallery for Pics.