As seen in the photo below, the rear end of my truck is on a slight downward angle. It is easy to see in comparison with the second photo of a different F-150. What I am wondering is could this be the body sitting improperly on the frame or is the frame itself off-kilter. Also what price range am I looking at to fix this in either scenario? Has anyone else had this problem?

 

Assuming the tire sizes are equal front to rear this looks more like a rear spring issue.

Could also be incorrect front coil springs installed.

Not too likely the cab or bed have been installed incorrectly.

 

I'm with JWA with this one. Doesn't look to an issue with the springs being worn out or broken. If something was up with the leafs there would be a lot less space in your wheel wells. Have you got under the truck and taken a look around? Something does not look right with that at all.

I can't really see from the picture but what does the space between the bed and the cab look like? Is it the same distance at the top of the bed as it is at the bottom of the bed?