You have two options, you can either buy the panels direct from an MB dealer or you can check
http://www.kkmfg.com for prices. They make replacement Mercedes sheetmetal panels and are supposedly very good, and not to mention inexpensive. Hope this helps!
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Rgds,
Aaron Greenberg
MB technician
Precision Motorcars, Cincinnati, Ohio
'67 250SE Cabriolet
'77 450SL
'79 6.9 (SOLD)

'80 300SD
'85 380SE
'89 420SEL
'93 300E 2.8