Matt,
If I recall correctly, the A150K, L & M are able to STC the Lycoming O-320 for the 150 HP. But, the L and M models lose their aerobatic certification. Apparently, the K model keeps its’ aerobatic cert due to an oversight on the STC. The book on single engine Cessnas talks about how putting the heavier engine on the Aerobat negatively changes it aerobatic qualities. Not nice. So one would be legal to perform aerobatics in a A150K O-320 conversion. But you’d be in an airplane trying real hard to bite you.
