It wasn't very hard to put on, but then again I can have my axle out in under 45 minutes. I wound up cutting off the rear crossmember so there was only frame rail, cleaned that up, and welded it in place. I actually thought it should have been about a 1/4" wider,because the side plates don't sit perfectly flush to the frame rail and the bumper, but then again my frame is probably tweaked (as you can see I'm not easy on it). If you know what your doing as far as welding and cutting its not hard. If you don't like your body it's even easier, I actually just cut the body away so I could weld it.
As far as a fuel cell, the gas tank is just strapped to the floor in the back.
Up front I just have some mixed up stock packs that I've made up. I keep breaking leaves though and it's driving me crazy.