Don't get me wrong, not suggesting you drive around with A/C off in 115 degree heat. Just suggesting you check your A/C pump to insure it is free to spin as needed.(Its not like alternator, it will have some resistance, but it should move with medium effort.) Then test and monitor to see if the A/C is putting you over the top. (Putting more strain on the engine creating more coolant heat. Then taking 115 degree air to say 135 degree air behind the condensor and sending that at your radiator.) If a/c is putting you over the top can you turn off on the hills for 3-5 minutes till you crest and come down the otherside.
That does not take into consideration your air cooled tranny cooler and what that is doing to your air headed to the radiator. So a thought is at somepoint look at if your tranny cooler is heating the air to the air conditioner condensor, that is then sending super heated air at your radiator. (Causing a fail.) If you deem so perhaps you can arrange in a better way so it is not double heating the air. Or doing so in a more ideal part of the radiator.
Lastly if you find it is brief times your getting hot (2-3 minutes up a incline) I have found like the misters in the restuarants, doing so for your radiator works really well. Could be simple like a 2 gallon bug sprayer on the front seat and a hose to the nozzle in front of the radiator. It could be a junk yard window wiper system. (Just get one with more than a quart capacity.) It could be more heavy duty like a tank, pump, hose, sprayer, and switch on the dash. You do not want to spray a stream of cool/cold water at hot components. Rather a nice wide mist. It robs the heat off the metal very fast and I have found it seems to also cool the engine compartment. (But does not soak your components with water, think more like humidity.) We did this years ago on a trip, my buddies truck kept getting hot on the grades, we routed his window wiper wash hose with a drip line mister head, it allowed us to keep the truck cool towards the top of the grades and not have to pull over and wait or try to put cold wanter on the radiator and hope we did not create a bigger issue. We did so on a different trip pulling a friends boat trailer but used a bug sprayer from Home Depot. Both cases it was just to make the hills/inclines but would not be effective if your truck over heats on the flats too.