not sure if this was or could be part of your question but the "rim" sizes are not all the same in terms of offset. the lr3 and range rover "sport" are the same platform and thus also share the same rime offset, while the big range rover has it's own. thus rims are only interchangeable b/n sport and lr3.
you may not want to stick with stock sizes anyway on tires as they kind of look dinky on the lr3, possibly more to do with styling because even though the 2004 D2 had smaller tire diameters, they looked better in the wheel wells @ 255/55x18.
the lr3 is 255/60x18 or 255/55x19 stock michelin xpc, which is a very good all around tire by the way. i've done some crazy mud stuff in those but they handle highway rain and snow well too.
lastly, you may find if you dig far enough that most LR3 people are going with the Nitto Terra Grappler in 285/60x18 for off road while pretty darn good on road to/from play time.
personally i got a little crazy and got some 20" 10 spokes from the RR sport line and will have Toyo Proxes S/T's on them for 90% of my mileage. 285/50x20
