We all know volvo as Ford's safety conscious division but it turns out they have an extrodinary selection of wheels for their cars--most of which will fit the transit. The good things about using the OEM wheels are: they are generally high quality, made to stringent safety standards, available CHEAP from Volvo guys that are upgrading.
I got mine for $400 SHIPPED with 3,000 mile old tires. The tires are high quality all season Michelins that are rated for the same load and PSI as the transits' OEM tires despite the lower profile. MUCH quieter too.
These are 17" X 7" and the center bore was a perfect fit. Plenty of offset to clear the brakes.
Watch fleabay and Swedespeed.com --marketplace--classifieds.
The swedespeed forum even has an informative post with many pictures of OEM volvo wheels and their sizes/part numbers/names etc.