I found this really good site on d2's and I dont think its such a good idea to put 285 65 18's on a stockish d2. I wish that I knew someone who wanted to trade me 16's for 18's. Has there ever been a land rover swap meet? Where is a good place to pick up rims for these other than the dealer?
http://www.disco2.com/howto/offroader/tyresizes.phtml
http://www.disco2.com/howto/offroader/tyresizes.phtml