The floor is level, jack stands are level, very front and very back of frame rails are level. It’s just if I put the level just in front or behind the cab it slopes about an 1/8 to 1/4 from driver to passenger side....
So it's not twisted. That's a good thing.
I wish mine sloped to the passenger side. Most Chevy trucks lean the other way due to years of driver weight. If you have one that slopes the other way count your blessings!
Brings to mind the Model A coupe that was originally owned by a guy named "Tiny" who sold it to a skinny guy. He swapped the transverse springs end for end, and it then leaned right by at least 4 inches. I bet it still leans right to this day. That was back in the mid 60's.

Sounds to me like the springs might be the root cause of the slope?
He had it on jack stands on the frame, so the springs would be out of the equation.