What part of the country are you in. Do you have and Empire Truck shop in your area? They handle Cat products. that is were i got my coolant from. Not sure how much your engine holds. If you don't have your manuals do as I did catch the coolant in a container and put back the same amount. When you flush your system my manual states to do your last flush with distilled water.
Al & Katie
2005 Excursion 39L Cat C7 350 HP
Retired 33 years NOFD and survived Katrina