As far as I've been able to find, it's just a change in design, not a recall. I have the same yr/model as you, and had to replace my fuel distributor last year. If you haven't all ready, you should consider registering your car w/ MBUSA. They will send you recall information on your car - I've gotten two notices that MB is still honoring on mine.
82 300 SD
77 450 SL (gone)