Bilstein currently lists replacement shocks for the Titan in the HD line "Recommended shock for most applications, designed to work with the springs that came with your car." This a new listing. They also have shocks for pre-05 XTerras and Frontiers.
The Titan shocks list for $121 each but are avaialble from
www.allshocks.com for $67.95 each. I suspect that they will soon have HD shocks available for 2nd Gen X's and Frontiers. Replacement Bilsteins are guaranteed for life.