Just do something, Nate is fulla idea's (if you have a look on the R31 page you will see what I mean) but has done nothing yet!!!
RB30's are good with a RB25 head if ya gonna turbo them for the twin cam, if ya keepin it N/A then I wouldn't bother. After market ECU's (Wolf, Autronic) are good with the right one and the correct install and tuning. Standard air box vs pod doesn't make a hell of a lota difference. We have proved that on our 31 on the dyno. If doing a zorst, make sure if you are leaving it N/A you keep some back pressure, to straight through will only slow it down, not speed it up. Manual box and faster diff gears will pull you almost into a 15, it did with ours, we had a standard everythind else (box was standard 5 speed).