why don't you use the patch to bring your inventor model right into max, unless you have an older version.
there's a download in support for inventor, for this. It's for max 4&5, viz 4. but it's only for bringing in the invetor 6, and 7 files
http://usa.autodesk.com/adsk/servlet/ps/dl/item?siteID=123112&id=2525295&linkID=3016127