I wanna do a flush and fill on my 1992 Sixty Special before the winter weather and for the life of me can't figure out whether to put in the green Prestone or the orange Dexcool. Not sure what it has in it now but I do know that it hasn't been changed in four years while it's sat in storage. Also, do I need to get the pellets for this from GM. Oh, it has the 4.9 litre engine with 99,000 original miles. Thanks as always.