rear frame twist?

[z71bro96]

Just assembled the rear end today and I noticed that the left frame rail is higher than the right by about 3/4 of an inch. I noticed this when I got the truck from a friend (he got it from another guy and had no history) but I thought that is was from old springs and broken or missing shocks.

All new springs, shocks, bushings, crossmember and everything. Can't find any evidence of frame damage but I don't really know what to look for. Does anyone elses truck look like this? Thanks.