I usually try to refrain from tooting my own horn and I hate to do it in the forum but it is obvious no one here has heard of my company. If there is a problem with my posting this please let me know...
I own and operate Machined Aluminum Specialties and I have been making and selling aluminum rims with the adjustable backspacing idea since 1993...
I am the originator of the turned aluminum rim/photoetched center construction and have a VERY extensive line of turned rims. Using my parts you can build a rim to fit just about any tire width, diameter or backspacing you need.
Look here...
http://www.mas-parts.com/cart/indexf...whlcentrs.html
and if there are any questions please ask...