"Leveling the frame" on jack stands is a little tricky and more work than is seems. I am assuming the body and suspension is still attached.
If a long level shows the same bubble on the floor as the bubble on the frame, while truck is sitting on it's tires, you could assume the frame is level and suspension is equally sagging. Tires have same pressure. That may not happen. That would be a macro measurement. You seem to want a micro measurement.
What is your goal? Are you getting ready to do a modification? What is the purpose of "leveling the frame" on jack stands? If you just wanted to know if the truck was level'ish, that's easier. It was never dead nuts level when new. Give us a little more info/what's on your mind, then we can go hog wild.
Some of the comments seem to be more like parallel or racking checks, not setting a frame level on jack stands.
Also, the suspension would be out of the equation for leveling the frame on jack stands.
