Weight is only a part of the picture Juddy, you have to remember that the Isuzu motor also produces a lot more vibration than any land rover motor which I am sure would be part of the issue.
I know that hte wonf was certainly tested by the australian army (photos and information here
http://remlr.com/perentie_conversions_and_comparisons.html ) .
However I am no engineer to comment on one's suitability over another, simply passing on information that I thought was important. That said, in civilian life few of us would run at full weight in off road conditions where the most force is likely to be applied.
I have had (famously) a wheel fall off my series 3 at slow speed, and a tyre fail at high speed, and it frightens me to think what may happen having a wheel fail at speed.
Juddy, the LR like rims for trailers mentioned before are just for the trailers, not for the vehicles themselves. Interchangable yes, for long term use, not recommended.