Steve,
I recently placed an order from Mick Reeves Models in England for 2 6" WW1 wheels, a Vickers machine gun (1/4 scale) and a LeRhone dummy engine kit. Well he sent me two wheel sets for a total of 4 wheels, so I have a pair if you want them. They are 6" diameter, and you will need to make a bushing depending on your landing gear diameter. Cost is $45 If your interested I will post pics.
Good news too! BUSA announced that the Williams Bros molds and dies have been purchased by another company in Texas, and will be ramping up production of the WB wheels and machine guns sometime in May-July of 2005, if you want to wait.
Jake in Colorado