According to the manual it is a single green wire located in the main wiring harness (but I could not find it on my box, base, dai, 16 injector, plus racpak interface options). I may be wrong but I think someone said that the tach wire is only there if it is a box for an ls engine. Check with procrew he will know.
Joe, Thanks for the help. That question for other application, I have BS3 on mod motor and it's a stock ignition also i have aeromotive fuel pump controller and i want to attach the green wire of the controller to tachometer !! The question is there on BS3 output for tachometer ? Thanks again buddy