Originally Posted by
JDNSW
An overdrive is not likely to increase the maximum cruising speed, just reduce the revs at that speed. There is no five speed box that can be fitted without major modifications.
Most varieties of the Holden engine need an overdrive or some other method of changing the gear ratio, as, unlike the Rover engines, they are not happy cruising at high rpm for long periods.
A couple of further differences worth noting. Landrover 80,86 and 88" models have ten inch brakes. 107 and 109 have 11" brakes, and in the case of the six, V8, Isuzu engines, and very late 2.25 engines, the front brakes are wider. Most models have no power assistance on the brakes, although this was optional on Series 3 and late 2a 109, and boosters were fitted after market on some. Converting an 88 to lwb brakes is a worthwhile improvement, as is converting the narrower 11" brakes to the wider ones. If you like very light brakes, adding a booster is worth it, but it is probably not really necessary for most people. A late S3 dual circuit brake system can be fitted to any Series 2/2a/3, although 2/2a will need panel modifications to the inner mudguard.
John