what tyres you planning on running ?
if your going be running 31 inch tyres the disco box aint gonna like it....unless you open the fuel pump up, tweak the turbo and then itll pull just fine
and before all you start saying it wont....jim ( some people on here no him, martha,fuddy and disco v8) his disco stands on 33inch insas atm and it will outdo a 300tdi 90 on 31 inch bf muds,
but he has got a full width cooler like me
but back on topic :lol:
you could always fit the disco transfer box and just see how it goes, if you find that your always in 4th and cant seem to ever get 5th, tweak the engine (sensabily) and then see how it goes, if not refit the defender box.
i used to have a disco box in mine ages ago when 1st built and ran 31 inch grizzlys, and i could never get 5th...tweaked everything and got a 5th gear then i added a sh** load of weight onto it modding the whole landy and then i lost 5th so just changed the box
dan