I have a Leupold 3x9 Veri-X II on my Lyman Mustang Wind Drift. Darn nice scope. If you already have one you're not using on another gun, put that sucker on your inline and don't look back. Why would you want to buy another scope?
I have Simmons 4X ProDiamonds on four other muzzleloaders (one inline and three sidelocks). A 4X is all you really need for anything out to 200 yards.