I'm doing a mini-me on my D15B7 (swapping the head to JDM VTEC D15B SOHC)

My old 1994 Civic DX 4DR doesn't have a tach. haha.

I can run a wire for the gauge from my new P08 ECU right? Also is there a guide to setting up a RPM activated VTEC switch? or installing a VTEC controller?

 

First of all, you probably won't need a VTEC controller unless the motor's built, or you're not familiar with tuning. You'd just be asking for trouble if you started messing with that.

Secondly, your DX has a wiring setup all ready to plug-and-play the other OEM cluster that includes the tach. Take a look at some wiring diagrams online, you'll find out which wires you need to splice in order to get your tachometer working. You don't really need to go through all the trouble of directly wiring the ECU if you take this method. (speaking from experience as a DX owner with no freaking tach.)