I'd say a minimum 150 hp, without knowing heads(I don't feel like looking them up). It's probably more like 160-180.
Lose the magneto and the tall stacks. Put shorter stacks and real air filters on it.
I have a 2165cc, AS41 mag case with 78 crank and 94mm barrels. It produces 180hp. I did a top-end rebuild at 45,000 miles. Oil pressure is great and bottom end is good.
The most important thing is that the bottom end is BALANCED to prevent wear. Also, minimize time above 6000rpm. I'd bet the crank is counter-weighted so that lessens wear also.
With that much hp do I need to worry about tearing everything else apart? Can the current drive train handle it?