Bill,
Have you satisfied yourself that the rim width can handle the particular tire?
Take a look at
http://www.extrem-motorsport.de/index.php3. They have an English section and they are a very helpful group. There are mixed tales about getting their parts stateside. I am certain that they run and have helped rig vehicles with the tiresize you are looking at. They and Europa do have the taller springs if needed. If your rack crawling I suspect, ride and comfort become of lesser concern,
Good luck.