AQ131 camshaft should be an "A"?

[dennis461]

I started tearing down my B230 engine with an AQ131C label on the air cleaner(spark arrester). I found the camshaft has the letter "M stamped in the end, so
I'm guessing a previous motor swapped a car engine. I've seen "A" camshafts on e-bay so it looks like I will be spending more money on my boat.

Should I get an "A" camshaft or is there a better choice for a bit more horsepower?
I've already started looking for valve shim suppliers.