Mark most everything from the short blocks transfer to the new case. The bearings in the short blocks are number 6201, pretty common. They are open or not shielded or sealed as there is a seal that presses into the case from the outside of the engine. In the new case you only need the seal at the front of the engine as the rear bearing is pressed in flush with the case. The case isn't machined through in the rear bearing support so you need to cut the crank off a barely proud of the outside of the rear bearing. May need to test fit the crank back there to make sure it doesn't rub the inside of the case. The front support should take the same size bearing. I will be useing a shielded bearing there. Shielded meaning there will be a metal shield on both sides of the bearing. I think this would be better than the rubber seal. Besides I don't think there will be room for a rubber seal anyway. I get my bearings from the local bearing hous Motion Industries. Any supply house can get these bearings. Tell them you want a 6201 bearing but the shielded version and they will fix you up. Don't know what 50cc reed engines there are out there but Echo makes several 30 to 33cc reed units. Also don't know that it has to be a reed engines to make one work. The Echo CS-346 is a reed engine with a standard piston. No window etc. The engines you will have are the same way. Also I don't think the other RC manufacturers are using special pistons in their engines. Most are Echo, Stihl, Husky, etc. cylinders and they were not reed engines originally. My Echo 61cc twin has regular pistons too. Also if you are open to other CC sizes you may be at something over 100cc. Making a case would take some time without CNC equipment but would be rewarding. You could make the crank the same way. May be a little heavier than some but not that bad. BME has used stock Echo cylinders and pistons for years. His cranks were and or are custom made though. Nice work can be done with a manual machine, a rotary table, and an indexer. I have seen a Volstro head for a Bridgeport machine like mine do incredible work. CNC put them out of business. For a home shop guy though they can be the ticket for CNC type work. I would get one in a heartbeat if I could find one. Well I have found them but the money is stupid. One will turn up though. Patience.