Calling all "older" Nissan Nerds

[RetroBistro]

Please excuse the dramatic heading! I am a newbie to this forum I confess my addiction to time tested Nissan vehicles, and I don't see much chance of getting over it! I have two Vanette's one 2.4 diesel off road and one 2.3 diesel on road, My quest and question to those of you who know is: getting a higher gear! ie is an add on available? or can I bolt on to my existing engine a Terrano gear box with disabling the 4X etc or is there a gearbox hack? Many thanks for your attention.