Tweaked Frame

[hchad18]

I've had my truck with the bed and front clip off for a while now and just recently checked the straightness of the frame. I jacked up the front to level and then checked the back and I am down about an inch. It is progressive it doesn't just drop at one point. If I level the rear then the front is out. So what I'm wondering is if these frames are known for being a bit out or if I've got a real problem. I don't see any signs where damage might have occurred or where someone might have tried to fix it. Thanks

Chad