Consider rebuilding the head that is on the car now. It is lower mileage @ 175K, not overheated, probably never been milled and definitely the right one. Have a valve job done on it, replace worn guides and it should be like new. This saves the expense of another head, reduces the chances of getting a bad one and has a fresh valve job.

Find a shop that does Mercedes diesels in case it needs to have the pre-chambers removed if it needs to be milled/planed. Confirm they know the minimum allowable thickness and that they measure it before and after milling.

Good luck!!!

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer