The easiest way IMHO to do this is to buy non drilled 10 inch ALKO parallel hubs and have a machine shop drill them 6.5 x5 and fit Land Rover studs.
You check the depth by comparing with the studs on your D1 hubs.
The LR studs have to be countersunk to a depth so that the emerged length is the same as on a D1/RRC as the Alloy nuts are closed.
This took me about 3 months to figure out.
BE VERY CAREFUL that you do not buy ALKO parallel hubs with LR pattern as they are IMPERIAL and the holes for the splined section of the stud are too big for LR studs.!!!!
Of course you can run steel wheels on these no problem but not alloys.
The other question I have I guess is whether D1 alloys are located by the centre spigot and how big the hole is , and subsequently whether it will fit over the ALKO hub nose which is very big and deep.
RRC 3 spoke alloy wheels fit no problem as they were never located by the centre spigot and are deep enough to clear the bearing carrier.
If I were you and the purpose is to have a second spare like I did, I would use RRC 3 spoke wheels that will fit your D1 and are the same size and offset.
Regards Philip A

