Deaver +2 is stock ride height, but call them and tell them how you use your truck then they will guide you to the best option for your use. It’s worth the call and they are really good people to work with ask for Scott.
Running 37” I would be looking to go to the +3. Raises the rear 1” and your icon kit should have enough range to level the front.
It’s most definitely the extra weight you are experiencing on each corner. I noticed it with my wheels and ridge grapplers immediately and I still have 35’s. Deaver +2HD and R1 BBK are being made for me now. I also have the icon kit. Next will be new shocks and then maybe I will go to 37’s. Only if I’m confident in the handling but I really don’t need them for my use or want to open that can of worms!
Weigh front and back axle. Grab a tire chart and see
what pressure caries that load. That will give you a
minimum pressure. 35 front , 32 rear on stock tires
Is what I am running. BUt you have to know weights.
OR chalk the tires and see how they lay
I run 28psi anytime i'm going offroad. Grabs the road like a dream. you could even air down to 20psi. nay lower than that and you should consider beadlock wheels. I run down to Baja on a regular basis and typically am doing 60-90 down whooped out baja roads.
When you say "unstable" what exactly do you mean...is the front darting left or right, is it pulling to one side?, if you let go of the wheel does stay straight?....
Tires can be an issue, yours might be Load Range "E" which is really stiff becuase it was intended for a much heavier loaded truck. To get thosr tires to behave somewhat I'd be letting the fronts down to about 34 psi and the rears to about 30....
you'd be amazed at the otherworldly difference when going from 28 to 25 psi in the dirt.
driving off-road is "loose" and if you aren't wise to keeping yourself in control and stable in the dirt, it might be the wrong hobby for you. sidewall flex causing "sloppy handling" at speed on loose gravel? are you f'in kidding me? use the gas, rotate the truck, have fun. this isn't road racing.
If you can afford a raptor, you can afford a $200 viair portable compressor to air your tires up if being below 40 psi on pavement terrifies you. Just drive the truck offroad at the appropriate air pressure, then spend the 10 mins airing back up before you head home.