This motor will respond to the same changes as any other OHV motor. The problem is that there are no off-the-shelf parts like there are for the more popular motors. If you're going to use this motor regardless, then possibly the best way to increase power by 40-60% would be with forced induction (centrifugal supercharger/blower/turbo(s). There will be a limit to the power/rpm's the motor will tolerate, with the weak link being the valvetrain, pistons, rods, crank or the main bearing webbing in the block. One or more of these will lay down on you at some point in your quest for more power.