Alternator dilema

[DM72C20]

In the same boat with my swap: 09' Silverado Gen 4 4.8 donor motor and trans into 72' C20.

I am planning to use the GBCM and have it in place on the negative cable. Computer and wiring are all from the donor truck and modified as needed.

I thought I had it figured out after reading the tri-five thread about using a PWM controller to alter the signal to the alternator. I picked one up for $17 figuring it wouldn't be the end of the world if not needed. Reading this thread and Nova's reply makes me think that the PWM gadget isn't needed now..

In the ls1tech link I read this from Hart Rod: 2 wires to the alternator, 2 wires to the battery, 2 wires to ground, 1 wire to serial data port - BOOM!!, it works!!!!

Not too sure where that serial data port wire needs to be connected?