Larry,

I too have been looking for a rear seat to install in a '75 450SL and have found a company by the name of World Upholstery (www.worlduph.com) and they have the rear seat. In MB-tex the non-folding is $370's and the folding model is $650's. It is actually a bucket style seat with center divider. There is a good photo on the web site.

wd40