What Dan said. Other than the actual case casting and the index, the small and large index D18's use all the same parts and the speedo gears should interchange. The only exception is the intermediate gear teeth counts/shaft sizes but that would not affect anything other than the intermediate/bull gears.
1955 CJ 3B, 381cid sbc (441cid all aluminum sbc coming soon), AGE M22W, Teralows, Warn OD, OBA, Premier Power welder, Warn 8274
1968 CJ 5, factory 225" w/ headers/450 cfm Holley, T86AA, Belleview winch, Warn OD
2012 Wrangler Rubicon Unlimited, Warn 9.5 xp-s winch