If you need a quick, cheap engine, Go for a used YS 61 long stroke two stroke engine. Its got the YS fuel injection, and is very powerful for its size. I had the rear exthaust one in a 60 size Desire pattern plane with Hatori pipe, and was an awesome flier! I would recommend YS for any performance applictation.
As for Saito? Save that for a Piper Cub
Good luck