your not limited to the nissan crank angle sensor, i forget which one it is in particular, a toyota unit I believe... but it is possible to run another sensor that is smaller. Like mentioned, you can clear the firewall, thats not the biggest issue. The largest problem, if you can call it that, is the oiling supply and return for the head. This topic has been covered in depth, even with visual aids on the sr20deforum for those who are interested into looking further into the subject.