Honestly, there's no better way to outfit your rig than to use it and figure it out for yourself. I started with small trips back in 2016. When I come home I ask myself what I'd have liked to have had on that trip and I bought it. You don't really NEED much, it's more about comfort and wants. With that said if I had your truck I'd be in the market for skids, sliders, traction boards, compressor, and deflators.
Sorry for the Wall Of Text but here goes...
Yep. Take some trips. Decide what you could use. Most recently, I started out with a 14 GMC Sierra with a soft tonneau. It was nice for keeping things mostly dry and out of sight, but wasn't truly secure. I removed the tonneau and got a diamond deck tool box instead. Loved it.
...BUT...I'm driving out through the Badlands, Tetons and Yellowstone in October and plan to do a lot of camping, so I removed the toolbox and put a Leer model 180 cap on the bed so we can sleep back there in rougher weather. Crap! Now I need another place for my tools and gear! So I have to get or build a deck and drawer system for the bed.And now I'm adding a roof rack in top of the Leer, so I have a place for my Kayaks and such.
My equipment has evolved over the last year or so.
About the equipment Diabetictako mentions. Everything he said can be useful, and some of it can be a little costly. Not to diminish any of it, but I'll offer budget alternatives and some stuff I like do take on long trips.
COMPRESSOR I think it's always wise to have a way to blow air into your tires, although a foot pump will do if you dont mind time and exercise! I have a foot pump in the Jeep and a small, rechargeable batt operated compressor in the Sierra.
DEFLATOR A deflator, for me is anything I can jam to the stem to release air, and periodically measure with a tire pressure gauge. But the deflator would be nice.
SKIDS. I have a Z71, so I have some sort of skids, but I will say that my 93 non z71 K1500 Blazer Silverado had much better and real skids. I think they are a great idea especially if you removed that chinstrap under your front bumper. The z71 has the added benefit of an increased capacity air filter and offroad tuned suspension.
I personally always try to get a truck or SUV that has a factory TOW package. You get the slightly added frame rigidity - often making a protective cradle around the fuel tank (Jeep Grand Cherokee, Cherokee, Big Blazers, etc) - and usually TowHaul mode shifter and increased oil coolant, etc. And front hooks.
Rock SLIDERS I dont really use. I imagine if you are going through really rugged territory you might want them. My lady is short, so she really needs the running boards to get into the truck, so I stick with those knowing they have reduced my "off-road capability."
TRACTION BOARDS. Well in places that see snow, we always want something in our car or truck that will help us get out of a slippery spot, although younger kids dont tend to think about these things in advance. If you dont have the cash for the expensive ones, just gather up a couple long strips of carpet, 2 to 3 feet wide each, maybe 4 ft long. And keep a few scraps of wood in the back of the truck, and a recovery strap. If you know you will be off road, bring a spade shovel.
GPS is great. I have an older Garmin. I like to keep an Atlas and maybe some local paper maps or Gazetteer with me, though! If I have them, I keep the Tyvek maps of the state or state park I'm in or around. They show roads and elevations, too, so that helps. Get them at REI or if you are a part of Appalachia Mountain Club or something. I wouldnt mind having one of the 6 or $700 off-road GPS units, I just dont have that to spend at the moment.
I have the bedrail LIGHTING in the back of my truck. Augmented by the light inside the Lear Cap, I see very well back there. I want to add outside lighting to the Leer cap for camping, and maybe som KC type for driving. And I keep a flashlight or headlight.
I keep a sheepsfoot style serrated blade RESCUE KNIFE in the center console should the unthinkable happen and we need to cut ourselves out of our seatbelts. I carry one when hiking or kayaking too.
Always bring FIRST AID including a SPACE BLANKET for warmth or shelter
FIRE. Always have something to start a fire. Ferro rod, matches, lighter, what have you.
Bring TOOLS that you need specifically for your truck. Thats very important! Find out the sizes of all the nuts and bolts for all of the important or commonly changed or fallible parts, and bring those sized tools and some adjustable tools. So, the lug wrench for your wheels, the size driver for your battery cable nuts, oil drain plug, verious under-hood faster sizes, a flat head and a Philip's head screwdriver. And a crowbar. That way you dont carry 25 wrenches, none of which fit any nut or bolt on your truck. Diamond deck cross box (to which I have attached my Coca Cola bottle opener) or a purchased or home made Decked System to store it all.
I usually keep a Leatherman and a Victorinox Swiss Army Knife in the truck as well.
I always carry JUMPER cables but am going to switch to a batter jump pack.
FOOD & WATER for a couple, 3 days of emergency. Not a feast, just sustenance. I get some Mountain House meals from REI or WalMart. Dont forget for the dog food if you have one. I also carry a fishing pole. For fun and it could be useful. I have a couple gallon jugs and some Nalgenes. Sawyer filter would be nice.
To that end carry a small butane STOVE like the Coleman Peak1 or the Primus Classic Trail stove.
For that you need a metal container to boil water in, on said stove. Full army canteens come with a metal insert inside the bag, to use as a cup.
Some hand SANITIZER.
COMMUNICATIONS . Cell phone chargers. I personally have a CB radio and a small handheld FRS/ GMRS radio. With NOA weather is always gonna be worth it.
CLOTHES. Just one change of clothes, an extra jacket, winter hat some GLOVES (lined work gloves like the Klein Tools 40018 are a good all around choice), extra pair of work boots. Just in case you ever falling and get wet and need to change so you dont freeze.
On long trips I always bring a BLANKET or SLEEPING BAG.
If you have a diamond deck cross style toolbox or a decked system in the back of your truck, most if not all of this stuff should either be attached to your truck somehow, or fit in the toolbox, leaving plenty of room in an extended or crew cab truck.
ROPE. Always have rope and paracord. Or a lot of boot laces.
TOILETRIES in a shaving kit. And dont forget to bring a TOWEL. One of the single most useful and versatile bits of equipment you can carry. Sure, you can dry off with it but you can also use it as a blanket, a hood, a sunscreen, you can soak it in vitamin water and chew on it as you walk, you car fend off knife attacks and snap someone's behind with it.
That's just about it.