Back in the day, I owned a beautiful '79 Ford F250/460 with the C6. It didn't like AC on while towing up the Grapevine on I5.
Modern vehicles have so many PCM's and BCM's that it's just about impossible to overheat without the computers commanding a limp mode to save the drivetrain.
What are the spec's on the OP's GMC 1500?
2018 Ram 2500 Tradesman, CTD/CC/SB/4X4/Equalizer WDH
2019 Forest River Surveyor Legend 19BHLE