So many places it could be coming from that it isn't funny at all.
Windshield, Cowl drain, hood hinge pocket, window seals, door seals, sunroof seals, and sometimes even less obvious places like the evaporator draintube and rubber seals around the wiring coming into the cabin.
Water can build up fast, and takes a long time to dry.
Dry it out, remove carpets, remove kick panel under drivers side dash, and have someone hit it with a hose while you lay inside. One of the sacrifices of owning an old luxury automobile. I still have yet to do this on my new find.

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