I have one sitting here. Is it worth building. i also have a NIB ST GS 40 and a pitts muffler. will that be a good enough combo?

You bet, I have there SE-5A Biplane 46 ARF with a 1984 OS 61 four stroke and a straight header
pipe. Great flyer and the engine mounted up right all under the cowling sounds like a harley.

Ok then ill do it.