Body to frame alignment

The easiest way to tell if you're crooked is to look in the rear inner fenders. They are right at the same width as the frame.

Basically you just run you fingers over the 'joint' on both sides and make them match. (That's an important step if you're wanting to run the widest tires you can find). If your body is off, that's a quick and easy test to figure it out.

Your bumpers being off is pretty normal. The mounts are slotted and they make shims to square them up to the body.