Fred
I try not to get into the brand wars but I have to assume the there is more to this than one being a GM 1500 and the other being an Eco-boost… and there had to be a better alternative on you 85 GMC…
I have no doubt you and your sister had the problems… Maybe insufficient capacity from factory or a flow restriction of some type…
I have hauled a lot of heavy loads on steep grades without even a hint of overheating at all… haven’t had cooling problems since the 50’s and some serious vapor locking with issues in a International 549in the late 60’s… if the truck is ordered as a daily driver with a single row rad, maybe there would be these kinds of problems, but I have always had the option of a high capacity or heavy duty cooling system... I have always used a external tranny cooler and engine oil cooler for towing, and never had to worry about overheating problems…
OP you should be able to climb a tree with your new truck…