Help broken jd 318 onan

Thanks for the advice guys. I think I will attempt to repair the existing motor as it did serve me well for the last 14 years i owned it. I bet it didnt get the oil changed a half dosen times over the last 14 years. Supprising enough the crank and block measure up good. I cant believe it, piston bores within .0015 top to bottom and round within .001. Crank measures within .0005 round on all fits. I am having trouble finding a replacement piston and rod. I would like to only replace the broken parts , rings and bearings. The spacer for the flyballs is also a problem as I would like to reuse the cam and gears. I cant find a spacer and will probably end up making one. Im thinking it should be a press fit to the hub so it spins with the crank and gear. I was thinking of making it out of bronze. Any suggestions? I dont want to use plastic. I heard someone say the early ones were steel. Im guessing they were Cast iron if they had problems with them breaking. I hate to put a old one in even if it is not cracked now. Im afraid it will crack and cause the same problem again. Blown motor from runaway RPMs. Any one ever made one and did it work?