OK, the traction bars are pretty close, that was covered in another post just recently, like in the last few days.
There is no substitute for keeping the shocks outboard. If they're inboard, you can make them stiff enough to control roll but then they'll ride rough. Running them outboard lets you get the best mix of bump control and roll control. It really is a big deal in how the truck handles. You can probably get a long enough shock in a location close to the factory setup, measure it up and see what you can fit in there. If you can fit a 12-14" shock in the stock location, or close to it, you're done.
Flex with the traction bars comes down to length and angle of the bars and the length of the springs. The setups we've done so far had minimal effect on the suspension. One setup we measured out here with the forklift lost less than an inch from the "no-bar" configuration. This is measuring how far we could pick the front tire up before another left the ground, we were getting 40-45" up with and without the bars.