Hi everyone. I have read a lot of posts here and elsewhere and got mostly confused so here are some questions to start my posting here. I have a 2004 Sierra 2500 HD 4X4 6.0 auto and want to put a new (to the truck) PCM in it. Do I have to get a pcm from a truck or can I use one from a car. I know I need a drive by wire one. Is one better then another? I would like to use one from a vehicle newer the the 8 year old one i have. I have read the one i have is not the preferred one in a car. What do you suggest? Then what about the OS? Should I use a stock one or would a custom one be better? If so which one? TIA for any suggestions.