When I got my 84 500SEL the pump in the trunk was missing. The car had ortho (sp) seats that uses the same pump. The only pump I could find was from the dealer and it cost far more than I paid for the car.
I ordered a power door lock kit from JC Whitney. It came with 4 actuators and associated hardware. I just removed the vacuum actuators and installed the kit. I then wired it into a remote keyless entry. Also I mounted one switch in the console where the fader switch was (not needed anymore). I believe I used a power window switch. The car also had a security system and on the 84 SEL and maybe others there is an electrical trunk lock. I just wired it into the system also.
Works great.

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84 500 SEL (307,xxx miles)