Here's how far I've got with the same problem

http://www.peachparts.com/shopforum/diesel-discussion/285719-help-identifying-diesel-tachometer-reqd-want-fit-my-car.html

Earlier tachometer for the cluster - adjusted the holder at the front of the engine - got me an amp - probably going to wire from the glow plug relay supply - got a bracket for the amp from a friendly chap on the forum

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!