The OEM UCA'S are identical Hoss 1 & 2. The difference is the shocks and the stouter axles, as well as the lower SAS gearing, lockers etc. You can peruse this site and find many who have replaced their Hoss 1 (Non-SAS) Hitachi Shocks with the Billstein yellow Hoss 2 shocks. It's a cheap upgrade, and was popular in the early years. More Recently, there are a number of aftermarket upgrade shocks, several height adjustable, matched to better UCA'S, which are becoming popular. Also a Ford Performance 2" upgrade for Hoss 1. Add in the reports of the reservoirs falling off the Bilsteins, and the reports that the Bilsteins do not improve ride quality, just add lift height, and it seems that these are a less popular upgrade now. If you're like me, and would have to hire someone to do the swap for $1,000, you're going to opt for a "better" shock upgrade.
