if you did swap the head over, it would need more than a light remap......
It would make sense to fit the 172 ancliliaries such as exahust, inlet manifold, injection system and pssibly the ecu....but you might as well swap over the engine....ti would be eaiser, then you could swap the loom in too.
BUT, you could run it off a new management system such as lumenition, emerald M3D, DTA etc.....this would allow you more freedom and ge the system perfect. But then getting a MK1 head with M! throttle would be easier as its not FBW, and you would not need to mess about with the throttle arrangement.
Make no mistake, this is not a minor mod.....its a huge one!