I am not sure about your 190 but in my 300e, if I remove the LF speaker that would give me access to the cluster.
One more thing, the speedo cable goes down and it is clipped to the firewall next to the steering column. If you unclipped it (if you have not already done so) that may give you the extra room that you need.
If that does not work, just disconnect the cable from the transmission first.
Good luck!:p

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J.H.
'86 300E