Please note the early Range Rover (upto about 1983) 10 spline diff had the oil filler plug in the diff as opposed to in the axle housing like the later vehicles, if you need this early type please be sure to mention this when ordering.
The stock diffs are not particulaly strong if you are a regular off roader, the usual failure mode for these 2-pin diffs is friction welding of the 2 small sun gears to the cross pin resulting in the pin shearing and instant failure, this process happens very quickly when wheel spinning.
If you find you are breaking the stock diffs regulaly I would suggest looking at either the 4-pin diff or a limited slip or locking type.
If you are unsure if you have metric or imperial diffs note that the diffs changed from imperial to metric in about 1983, the way of telling which you have is if you have a look on the head of one of the 4 journal end cap bolts and if you have '8.8' written on the head it's metric.