Hey Scott! Your 2008 Holiday Rambler Neptune XL is built on the Roadmaster RR4R chassis. For a steering stabilizer you need the Roadmaster Reflex Steering Stabilizer # RM-RSSA along with the Custom Mounting Brackets # RM-RBK6. The Roadmaster is the only option in this case but I would consider it to be the best even if others were available. If you need anything else feel free to reach out in the comments below. view full answer...