Another point from a US flying school prospective is the o-360 is about a bullet proof engine as you can get. This combined with their different age/TBO requirements has resulted in (at least one school) buying them and after 2000 hours replacing the cylinder heads and then running the engine to 4000 hours before replacing it. Such savings in running costs my make it commercially viable to upgrade to these newer models.
However from a UK prospective this is simply not the case.
