Echo 58cc "Short Block" (complete engine without accessories) #SB1020
http://www.smallenginepartswarehouse.com/parts.asp
On the "What to do" question, if you don't need the blower, I would convert it. You will have the satisfaction of doing it yourself, and use the money you would have spent on the other motors for airplanes or accessories! I think the power levels would be fairly close, with the Echo having a possible edge.
AV8TOR