I use a couple heavy duty totes. One for my stove, pots, pans, etc. Another for other strange stuff I don't need easy access too, extra fluids, extra toilet paper, paper towels, etc. Then I have all my tools in a fairly large, yet very study plastic tool box. Camping chairs go in the rear floor boards along with spare CV.
The rear seat bottoms come out also. If it's just me I pack the totes, cooler, tool box, etc. onto the passenger side of the truck and sleep on the driver side. If the girlfriend is with me then the totes go outside, under the truck or on the roof, and the cooler goes in one of the front seats. Our bags with clothes, laptop, etc. go in the front seats as well. I have though about building a platform, but it seems like it isn't worth it. My system works pretty well, and when I'm not camping I don't carry the extra weight, or loose the space. It is also nice to be able to sit upright in the back of the 4Runner, which I wouldn't be able to do if I had a platform.
As for weight, I had my truck weighed once a couple years ago. I had everything I have today, minus the winch and rear bumper. I was 5,000 pounds then with me in the truck, and a full tank of gas, plus my normal gear I carry.
So I'd say now I'm closer to 5,200 pounds without any gear. Throw everything I'd take on a long trip, and assuming it's just me and it's probably 5,500 pounds. Add in another person and easily 5,700 pounds. With me and 2 extra people like when I went to Moab, the truck was probably close to 6,000 pounds. I wanted to weigh it on my last trip all loaded down, but I didn't get a chance to.