Originally Posted by ForcedInduction

Engines after 1980 have a different cam profile for higher airflow that adds the extra 10hp. The difference between 951 and 952 is in the engine mounts and oil pressure sender, they are otherwise identical.

To get it up to 951/2 specs you would have to change your camshaft, tappets and retune your injection pump. Not worth the effort for 10hp.