Some crossover steering and rears up front would fix that clearance problem and give ya better feel and controll on and off road. After rears up front and crossover on my truck all I needed was to pound the seam flat at the firewall and I have not rubbed there since, even with relatively flat springs, low stance and fat 36" tires. I rember rubbing with 31s before. My tires do rub ,but they rub where the inner fender slopes down for the battery tray.
As far as the rear moving the axle foward means gas tank, and driveshaft issues. Modding the bed is the best solution if your happy with your wheelbase. A shorter wheelbase will give you a tighter turning radious, and better breakover angles, but a longer wheelbase means better on road ride, and a less tippy feeling on steep climbs.
