The original self-leveling suspension struts are hydraulic. There's a lot more to the system than just the struts, you have a tandem power steering pump, the load leveling valve, associated plumbing, gas spheres, etc. If the system has been removed and converted to a standard suspension setup, you can forget converting it back unless you like extremely expensive jobs or find a parts-car with everything you need installed. Typically the hydraulic rams in the struts are sent out for rebuild, not replaced.

The springs are different between standard suspension and self-leveling. If the self-leveling springs were left in place, the ass will sag badly, especially with passengers or luggage in the rear. The shocks are there to dampen wheel hop, not support the car's weight. If you have sagging-ass problems, consider upgrading to the "heavy duty" rear springs, they make a world of difference without compromising ride quality, if anything it's slightly better since the car rolls slightly less in turns.

For what it's worth, 200 pounds of junk in the trunk is quite a lot for any car, expect the ass to sag to a certain degree. If you're carrying bodies, considering asking the victims, er...passengers, to go on a diet first.

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Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]