V6/12s are a fun world to play in. I always wondered why GMC quit them except maybe the couldn't sell enough parts since they hardly ever broke down, and fuel consumption was another mark against them.
I could never really get a legitimate answer from anyone why GMC stopped producing the V6 as well as the 60 degree family of engines. I watched that period of time closely back around 74 and it appeared to be some sort of planned obsolescence that was from the hierarchy of GM and not the GMC Truck & Coach division. GMC Medium Duty Truck Brochures in 1974 did not list any of the GMC V6 or Turbium 478 Diesels, you could not find H, J or T 7500 series brochures at the dealers which were models that were exclusively powered by the V6. Yet when you would go to the dealer all these trucks in 74 still had the V6. To me I saw the trend of everything going to Chevrolet powerplants around that time as a reason of cutting production costs since Chevrolet engines were a lot cheaper
to make than the big V6's. I think even GMC historian Don Meyer brought that up too. When you really think about that it makes sense because the GMC Truck and Coach division never had produced an engine of their own from that point, their engine plant ceased operations in Pontiac Michigan
