I had emailed American Racing looking for some rims for my disco, and they wrote back pretty much telling me that American racing doesn't make products for D1's because of our (kick ass) bolt pattern.
Newer Range Rovers, LR3's, LR2's etc have a different bolt pattern that is easier to fit aftermarket rims.
I DID see a set on tirerack.com a few months ago, but who knows how accurate their fitment information is.
Your best bet is to stick with the rover specialist places.