I tend to think of the OEM shocks as throw-aways, they are usually the cheapest shock the manufacturers could find. Only exception is when they offer OFF-Road Packages, and include brand name shocks like in the Ford F-4 package they use Rancho, or the Chevy Z-71 package where they use Bilstien 5100's.
I have had the pleasure(?) of running alot of different shock packages on several different makes. I have used Rancho products several times , but never had any luck with their shocks. They have always failed due to leaks, and both times were under 12K miles. These newer RS9000, RS9000X, and RSX series I suspect are made a little better, I have not heard too many complain of leaks, or poor performance. I installed the Bilstien 5100 shocks several years ago on my Dodge, they were nice at first but failed with less then 6Kmiles. I replaced them with Bilstien 5150's, and they have been great. They perform like a shock should, limiting the rebound but easily compressing to absorb the bumps. I only have about 3-4K miles on these, but so far they are doing a great job. I will not be able to give a long term report, as I have already purchased 6 Fox shocks w/ remotes and plan on installing them this spring.
When most people talk about replacement shocks, I think they mean shocks with a purchase price of 50-60 each. For this money the Rancho RS9000 and RSX series shocks along with the Bilstien 5100 series and Edelbrock RSA shocks are all a good choice. I would stay away from Skyjacker, Pro Comp, Super Lift, and Fabtech for shocks, they might make great lift kits, but not shocks. The reason the offer shocks in the first place is their is a great markup in shocks, and offering them in their respected kits increases their profit. I also would not be afraid to venture out of the Norm, and try some of these above listed shocks. They are all name brand and quality shocks, and just might give you the ride you want. I got a bad set of Bilstien but it did not keep me from trying some of their other shocks. If by chance you decide to take it to the next level, and are willing to spend 100-140 per shock, their are some really good shocks available, many with remote reservoir. Some offer custom valving and the ability to re-build, but as with anything the better shocks with more options cost the most, many starting in the 180's and go up from there.
The 5100 form Bilstien, not much of a picture but you can see the Yellow bottom part of the shocks
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These are the Bilstien 5150 series
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These are the Fox shocks waiting till spring
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