I would do the free travel mod first. I bet its doing a see-saw when you drive, meaning when you hit long/deep bumps at highway speeds, the front bobs up and down because the rear has no travel and catches on the rear bumpstops.
You all should still put in the z71 bumpstops up front.
And don't forget to put some aftermarket bumpstop on the axle or frame when you cut off the rear bumpstop bracket.
B