There is no spout for the diffs. Just a fill plug (near vertical) and a drain plug, on the diffs themselves. Diff oil is a pain to replace if you do not use some kind of pump type of container with a hose. I used to use a cylinder type of heavy oil hand pump (much like a greaser) but that was a pain to keep re-filling.
Last time I tried a large garden type plastic container with hand pump in the lid, (the generic kind that is also used for pesticides/ same type as the power bleeder) that you can purchase at any hardware store. I pulled the insecticide sprayer nose off the hose part, but kept the trigger on the hose. I filled the container, pumped it up, and presto, the 80/90W oil pumped into the diff. Didn't even have to stay under the Rover. It was a little slow in filling, but worked like a charm.