RM250 Identification and Parts Help

I am having alot of trouble identifying my bike that I bought. I bought it used and there was not alot of info that came with it. I need a new top end and don't have the old one to compare. My frame # is 32391 and engine # 32343. The bike I want to use parts off of is frame #38638 and the engine # is unknown as the case was sold long ago.

Any help with this would be greatly appreciated. If this is the wrong cylinder for my bike and you know where I might get the right one I would appreciate the info.

Thanks,

Mike