Just talked to them yesterday:

Call 800-367-6372 to order

Take a look at this link for a list of available material it is some what outdated and not everything is still available but you can find what to ask for.

http://hsb.baylor.edu/html/easley/autofaqs/mbusa.htm

Good luck. I'm looking at a 83 300D tomorrow 260K but it looks good and tight just got to hear it start and take it for a hell ride. If it passes that test I'll check the compression and start to negotiate the price down from the $1800 their asking.