Part of the issue, in my view, is the over stock of cars / trucks that are always at dealerships. They never sell their entire inventory,so they should only stock say maybe 50 vehicles or so. Then, if a customer wants a particular set of options / colors,
they can call around to find it or custom order it, like was done in the 1970's .. sure it takes a few weeks, but you get what you
want. And GM does not need to waste Labor Costs, Material, Energy. Transportation of new vehicles. They should also standardize on maybe 5 or 6 engines across the entire GM line. They would save in the long run and maybe, turn a profit.
