On my W123s, I often use the factory jack, as I find it's usually easier and more effective to lift the car and set it on jack-stands than the small trolley jack I have.
I use a spare Mercedes jack, that I keep with some of my tools.

A large trolley-jack might work better (in fact, I have one at my parent's home in Virginia Baech)
but it can be a real hassle wrestling with something that big and heavy, especially in confined spaces.

Happy Motoring, Mark

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DrDKW