the 3500 is runnin good and now i wanna hook up my 99z pcm to run the gauges. i started going through the wires to find wat is needed. my question is i was told the white wire comin from the icm (i have a 3500 but using 3400 electronics) to give the pcm a tach signal. but were am i feeding it to on the cav pcm? cant find a pin for anythin relavent?

There is a tach signal connection inside the relay center on the driver side fender. It should be at the end on the relay center closest to the front of the car.