Unless you will hauling a heavy front bumper with winch or a cargo track with generator, you do not need the heavier front suspension.
High idle option is useful if you have PTO operated devices or plan to run heavy electrical loads while stationary.
Dual or high output alternators allow you run a dedicated supply line to the TC and run your refrigerator or warmers on DC while traveling. If you add auxiliary lights and are driving slower, you will appreciate the the extra charging available to handle the load. Ford has auxiliary switches in the cab for electrical loads (upfitter switches) - I have one circuit connected to a 2000w inverter allowing me to power tools directly out of my truck without running the TC generator or when I do not have the TC on the back.
We have a manual rear slider window and will drive around town with it open, but once you get to highway seeds the road noise gets offensive and you will be happier running your fresh air vents or have side windows cracked open.
If GM has a camper package like Ford, it is worthwhile. Mine came with front and rear sway bars, upper overload spring pack, and TC electrical harness connection point. I opted to use the rear 7-pin plug on a Y-adapter because of fear of damaging an in-bed plug when hauling things in the bed other than TC, but the option is always available for me in the future.
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