Your best bet is to take advice from those who answer AND have a truck camper rig. The sticker on the door is for a stock rig. You already indicated you have after market tires, wheels, suspension, etc. The limiting factor is the axle rating.
I have the 2006 short bed diesel Dodge Ram w/4x4, 4 extra leaf springs on each side, air bags, 19.5 steel wheels, 14 ply commercial tires rated at over 5500 lbs each, yada, yada, yada. I haul my Lance 855S and loaded down, I weigh over 12,500 pounds with 7500 or so on the rear axle. I tow either a 5x10 trailer that weighs at least 2300 pounds or a Suzuki Samurai that weighs at least 2,000 pounds. The trailer is about 200 pounds of tongue weight on a 42" extension. Without the tow, I can and do travel all over the West at 65+mph without any issues at all. Towing the trailer with the tongue weight actually feels like a smoother ride. Probably because of the short wheel base on the truck. I towed my Samurai up and over Carson pass last weekend, topping at over 8,800 ft in elevation and this weekend I towed my trailer over 500 miles down from Sacramento to San Diego going over the Grape Vine at 4,400 ft elevation. The Samurai has brakes, the trailer doesn't and I couldn't really tell the difference, stopping power-wise.
If you are towing on relatively flat land, don't worry. If you are towing hills and mountains, just use common sense and allow enough room for braking.
Hell man! You got a Dodge truck! Act like it!!
