The welded up built-up crankshaft made me smile - that's late 1970s to 1980s racing motorcycle technology. Often used where they were similarly getting high percentage power increases. Those types of crankshafts were superceded on four stroke motorcycles not long after.
Prediction of increased climb rate in this case is interesting, especially with a fixed pitch propeller. More peak power in conjunction with a different cam generally means less mid-range rpm power. When climbing a high speed plane with a fixed pitch prop you may be well below peak rpm with throttle fully open. Higher displacement can offset this effect, not all planes have such a large difference between cruise and climb speed, and some have constant speed propellers. So it depends.