Poulan Pro 46cc engine will fly that airplane perfectly. For an 80" Cap 232--I would recommend closer to 50cc size engine. The worse thing you can do to an aerobatic plane is starve it for power. No bigger sin than building an anemic aerobat.

Conversion engines work just fine. I know, because I've actually DONE it. I've done TWO Poulan 54cc with electronic ignition. Yes, I did that motor twice. It runs that good. I've done a Craftsman 38cc. I've done about 3 or 4 Ryobi 31cc engines. I've done a Makita 45cc engine.

You can put electronic ignition on the engine to save weight and make for easier starting. It will still be hundreds of dollars cheaper than any commercially available engine. Or, you can run it on the magneto.

Some commercially available engines that also run on magneto ignition:
Zenoah
Quadra
Evolution

Thousands of guys put these "overweight" magneto engines on aerobatic airplanes all the time. It works fine.

Go over to the conversion engines forum and start reading. Those guys have done all kinds of aerobatic planes with conversion engines.