Hi Fastpepper. I think your best bet is to get a replacement .32 Dynamite. I just saw a new one go for cheap on ebay. Retail I think there $120. An O.S. .32 puts out a little less power and thats if you can find one. Next option being the O.S. 21 race engine that I think you kinda got your eye on will need a starter for sure and I doubt you will be able to use your old flywheel ,collet , mounts or exhaust system. I'm going with the O.S .46 for my SW , but it also is requireing a complete redo. Ron suggested a Novarossi .28 to me as well. Really nice but kind of expensive. Check out a coulple SW threads on this site, there is talk about a guy who can rebuild and mod a .32 Dynamite for a reasonable price.
I'd like to see you put that O.S. .21 in it and post us all on the results. It was my second choice and I'm curious.
Come on Fastpepper, you know you want it !!!!!!!!!!! hehe