That airplane is the World Models Super Sport Senior with different covering. It is a great flyer, but it is very light (read that as not very sturdy). It flies very well on a 91 four stroke. A 1.20 four stroke is way more than it needs. (I have flown it with both, including on floats with the 91.)

A gas engine won't fit inside the cowl, and you would probably have to reinforce the fuselage to handle the vibration. Not to mention the balance problem.

It's a very nice airplane, just not very appropriate for gas.

Jim