I went from Rancho 9000 adjustable to Bilstein's . I think they are # 4600's with blue covers.
Both were a great improvement over OEM's . I found that the adjusters on the Rancho's became corroded over time due to heavy road salt ( but that took a few years and 50k miles ). However , the quick n easy twist of the dial on each shock made the ride fine tunable, unloaded truck vs loaded truck. Setting range from 1 to 9 ( 9 being the stiffer ride )
Both shocks work very well and made the ride loaded or unloaded, a real 'smoothie' .
correction...I do have the 5100's . not 4600's .