I'm to the point in restoration of my 81 that I'm looking at the cruise control. It came factory with a vacuum servo missing the control module. I do happen to have a newer stepper motor controlled servo with the control module from my rust bucket 1982. Is there any consensus on which is the more reliable of the two? I'm not fixated on keeping the car 100% original since I don't have the original plate and data cards.

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1978 Mercedes 240D
1981 Mercedes 240D
1982 Mercedes 240D