Yes, SLS is a bolt-on option. It may even have been installed in the odd sedan. BTW, try to get a late-casting head to install on the 603 while you have it out (if it doesn't already have at least a #17 casting). I believe Mercedes went up to #22 before they quit tweaking.

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970