Blue, white can be removed. Brown can be removed as well if you are using the PCM pigtail. You do need power to the firewall block which the red wire supplied in the stock wiring. I kept my ammeter, I wanted stock look and function. In the electrical forum there is a long thread from VetteVet and others going over different options. My build thread has a diagram of how I did mine if you want to reference it...
http://67-72chevytrucks.com/vboard/s...d.php?t=796095