Im using the magnum 91 4 stroke and its plenty of power.

with a 13x8 prop its pretty quick, with a 14x8 its much more scale like with great vertical, and the sound of the 4 stroke makes it perfect.
I cant imagine this plane with a 2 stroke sound coming out of it, but I were to do it, my first choice would be the Tower Hobbies .75.
The size of a 60 with extra punch and idles like a dream.