The series 2 and 3 motors all share the same camshaft, however the naturally aspirated motors and supercharged motors have different cam timings set in the cam sprocket.

From those pictures it is easy to see that the L67's cam alignment mark is slightly further clockwise than the L36 cam sprocket. Some have measured this difference and have found that the L67's cam is advanced by 2 degrees compared to the L36.

Each has different part numbers for the timing set and the cam sprocket. However, the crank sprocket is shared between them.

In theory, switching to the L67 sprocket will cause the peak horsepower to occur ~100 rpm sooner than with the L36.