Thanks for the replys. The thoughts were I have looked into it a little and it seams on the 172 setup I need to have a block brace for the high power output, the throttle bodies I like to use AT, they are 45mm on the 197 instead of 42mm on the 172. Clutch and flywheel are bigger, Crank is lighter and is also made to take a lot more power. Not sure where the rear engine mount looks like and weather it will be the same as mine (I run a Sadev st-75 ).
I have 2 engines at the moment which are both around 225 bhp and 230 bhp that I would rather not break up, so if I'm starting a fresh high spec engine which base engine has the most potential.
Water pump etc then would not be a problem as I would prefer to keep the head and block together, unless someone knows of a reason not.