The 4 Star isn't the best choice for 3D. It does not have the large control surfaces required for performing "beyond the stall" maneuvers typical of 3D. The larger wingspan doesn't help any either.

However, if you are committed to using this plane, I would highly recommend a good four stroke, rather than any two stroke. Four strokes have better performance and a much higher level of torque in the mid range than a two stroke, and mid range torque is precisely what you want for 3D maneuvers (or any extreme aerobatics).

I would suggest something like a good used OS 70 Surpass. It's an extremely reliable, powerful engine, and should have no trouble pulling the 4* vertically. They can be had in the $130 to $160 range for a good used one.

You'll also want a large diameter, low pitch prop.
Dennis-