My motorhome is based on the TN van. I don't know the specifics on these vans only that mine 'was' a 409D before RMB of Germany did their 650s conversion.
AFAIK know it is the only Class A Mercedes in North America. I have seen quite a few TN and MB100 van conversions (like a Westy) but no full on Class A body-on-chassis like the RMB or Hymer motorhomes.
MB100 on Craigslist:
http://vancouver.en.craigslist.ca/pml/cto/2162958621.html
Similar externally but this one is a meter shorter than mine with a different interior layout (only the refrigerator is the same).
http://www.pistonheads.com/sales/1809728.htm
309D Westy in Victoria:
http://picasaweb.google.com/hectormini/MercedesBenzWestfalia#5392621067563346898