Update!!!
I went to my club auction and picked up 2 engines for this plane that for a total of the $120 I was originally willing to spend on the ST!!
I got a SuperTigre 90 (older Italian version) for $60
I also got an Enya 90 4-stroke for another $60.
Both are in excellent condtion...
Now I have another problem...which engine do I put on the Four-Star, and what one do I sell??