Gap between bed and cab is off on one side

[rally]

I haven't pulled the bed yet, so I don't really know whether or not this can be adjusted, but the gap between the bed and cab is larger on one side of the truck than the other. Considering it was cut down from a longbed, I think this might just be the way it is now, but I wasn't sure if there's a way to adjust that. It's not a dramatic difference, but it is definitely noticeable when you look at both sides.

Any way to fix this?