engine swap...

hi fellas, any of you who have read my previous posts will know Ive been having loads of trouble with my 2.25 petrol engine, Ive finaly had enough, so I managed to get hold of an ex military 2.5 N/A diesel out of a 1989 110, and want to put it in my sIII also ex military, now then, my landy is currently 24volt, what will be intailed in converting it over to 12 volt when I change the engine, and secondly what other bit's will I need for this engine to work in my series, will my current gear box handle the new engine, any info/advice is greatly appreciated

regards fenman..

lamps, voltage regulator, the engine mount on the drivers side is different(it fouls the distro pump, but one from the other side turned up side down apparently does the trick) and also a few studs are in the wrong place..