can you rebuild ethier of those shocks? If you can rebuild one over the other thats what way I would go.
the rancho's really dont look like it, look like they are the twin tube type.
the procomp's look like they are mono tube.thats what I would prefer.
dont get to caught up in the "knob" all it dose is close off the free bleds.
When I first got my truck, it had rancho 9000's all the way around with the skyjacker lift. The knobs did not change anything are far as valving went,cause with bigger bumps it did not matter if they were on 1 or 9.
but small stuff, like litle wash board, or how a concrete road is layed in section's you could feel the diffrence. between 1 and 9.....9 would make the truck chatter on the crete roads, chop chop chop chop feeling,during the first inch, and 1 would make the the shocks feel as they were dead for the first inch. Found 3 to be the happy medium all the way around...
but once you hit a little dip they felt the same from 1-9.
and here something to confuse you more on diffrent shocks types.
http://www.explorerprocomp.com/tech_training4.php
84project....3 billstien 5100's would be right up there with a 2.5 in
'volume".