Frame twist

[Mindl3ss]

After removing my bed I'm thinking my frame is a bit twisted. Looks to be about 1-1.5" lower on one side than the other, only in the rear. No buckling that I can see.

So I dropped by a frame and suspension shop to ask a few questions, but the answers didn't seem to make much sense.

Does the body/bed have to be on the frame? They said yes as they won't be able to make everything line up without it.

I figured if it's a simple twist (which I can't guarantee, but it appears to be) they could just use the factory manual spec and untwist it.

Second question, which I didn't ask because I know their answer, is it possible to untwist the frame at home? Any possibilities? I figure it would be worth the $300-400 to have it done, but considering the body isn't straight to begin with it doesn't make much sense to make it line up with the body. And I am a ways off putting it back together anyway.