I have a '74 260Z with an L26 block, and E88 head and 240Z style SU's. The engine has 153K on it and needs rebuilding. I want to increase the performance. Should I change to another head, or stay with the E88? If I stay with the E88, what kind of head job should I get? What else can I do to the engine to increase output? Cam?, different pistons?