Actually with big tires the steering stabilizer is needed both on and off road at all speeds above 20mph. And 2 definitely wouldn't be a bad idea for tires that wide.
Skyjacker makes an inline dual kit and I know I have seen the bracket kit for both dual styles sold separately. Skyjacker has a quad steering stabilizer set up too!
Rancho makes one as well but Im not sure if they make an inline kit.
You can buy red boots to match your truck and all the cylinders are usually white, but you could paint them if you wanted.
I used just a single Pro Comp ES2000 and it is definitely an upgrade from the HD Monroe stabilizer I had on previously. The Pro Comp cylinder was twice the diameter of the Monroe and much more resistance. I can actually feel it when I steer sometimes. But I only have 305/75R16s