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I really need a wiring diagram for instrumentation and/or that round plug on the rear of the cluster. 87 300SDL

Does anyone have anything? a link?
The frustration is overwhelming at this point. Which repair manual has good vacuum/wiring diagrams? I'll order another one if I must, I visited my local parts houses and the most exotic vehicle I could find books for are chevy trucks haha.

what I ordered was not what I thought it was and contains no wiring diagrams.

Please help if possible. Thanks.