$377 for an MB Branded battery even if delivered and installed is outrageous. Sorry I led you down the wrong path.
For grins, I checked the Interstate Battery website,
http://www.interstatebatteries.com/cs_estore/
and using their product finder for your car (application only goes back to '94), V8/5.0Ltr, their system came up with
Click here: Mercedes Benz SL Series 1994 V8/5.0L Automotive / Truck Products
List $163
Av. Retail $136
MTP-93
Mega-Tron Plus - 85 Months - 850 CCA
Double check the spec for your car, but this is about the price I paid for my Interstate. Good Hunting
Bob