Originally Posted by BillBoost37
Correct. About the only things that interchange are things like thermostat, plugs and you can use S2 coils on an S1, but don't want to do the opposite.
I would imagine those would interchange either way.
On later S1 models around 94-95, the fuel injectors are also the same. The S2 are rated at 22lb-hr while the S1 injectors are rated at 19lb-hr, because the S1 has a lower fuel pressure. Otherwise, I have confirmed that they *are* the same.
The valve covers might be the same, but I can't confirm that.
All in all they are two pretty different engines.