The topflite Corsair is right at home with any "60" sized engine. Not long ago (or at least I like to think 'not long') the engine I used in the Corsair was a ST-75. Perfect balance of power, prop and reliability.

Using one of the modern .90 size engines is an excellent idea. In fact, the ability to turn a larger 13" - 15" dia prop is a serious bonus.

The ST90, OS91, Jett 1.00 and a handful of others "60 size" engines are excellent choices - all very much right at home turning a bit prop.

Some of the slightly larger "90" block engines are good choices too. That OS 1.08 is a wonderful choice in this application. A ST2300 might work well too (sometimes you need the nose weight, so why not make it useful nose weight).

In general, you are not "over powering" the plane with a slightly larger displacement engine. The key here is good flight performance, which in this case is enhanced with the larger prop. Larger prop, throttle back in flight..... nice pleaseing sound and good scale performance.

Image I had available here is a Top Flite Corsair with a jett BSE-120L and turbo-jett installed.

Bob