There are many ways to build a roll cage. It is pretty much up to you how to build it, if you want to build one. You can buy prebuilt ones for little or now money. www.newera.com sells some roll cages. I know that someone on here has built a roll cage from bendable brake line and soldered it together. As far as a dual exhaust, everything I have read says they are worthless. They provide so little back pressure that you lose power due to the fact that there is nothing to hold the fuel in cylinder at the bottom of the stroke. Your best bet would be to put a tuned pipe on your rig.