If you buy a set of ST2 heads, you will have the following problems:
They fit good, except no output for the rev counter.
Do you want to replace your whole gauge setup?

If NO, do not buy ST2 heads. PERIOD.
Just a simple advice for anyone who wants to replace their 907 heads.
ST2 heads are not a simple fit. This info is wrong from finnpaso:
:
Surely they fit very easily, no anykind troubles....