Why don't I just pull over and shoot both of them with my IR thermometer . They can't cool off that quickly.
Isn't there a smaller pulley available for the water pump? That seems easy enough to try, given all the crap I've already done. The delta T will change with increased flow rate.
My recollection is yes, there are different pulley combos for a/c and non a/c and maybe for trailer package too. last pages in the cooling section of the shop manuals.