Ford 292 Y block rated Horse Power?

[SSsssteamer]

In 1956, Ford rated their 292 Y block at 212 horse power. By 1962, the 292 Y block was now rated at 170 horse power. Where did the 42 horse power go to? What parts did they change to down grade their engine's horse power? With rebuilding the 292 engines today, it could get a bit complicated if the 292 parts are not all interchangeable. What power robbing parts of the 1962 Ford 292 Y block do we not want to use? Thank you for any help on this request.