I used the lowest Talley one-piece when I set up my buddy's Montana with a 3-9X33. I can't remember if they were called Low or Extra-Low, but they were definitely the lowest Talley mount available and allowed for a 40mm objective bezel to fit without touching the barrel. The 3-9 has a slightly longer main tube than the 2.5-8, but I still had to flip the mounts so that they created the shortest possible space on a long action receiver. Not sure if the main tube on the 2.5-8 is long enough to span the gap between mounts. I would try the standard mounts first as they both look nicer and function better than the extended mounts. On some rifles (not all), the extended mounts cause a few difficulties with loading and ejection. I remember we tried the extended mounts on the Montana and had difficulties, so my buddy opted for the standard mounts and a different scope.