Look for an instrument cluster on Ebay or in a junk yard. I took the oil, water, and fuel part out of the new one I got which was from a 78 240D and everything worked fine on my 300D. The little cap thing in the middle of it is silver and the temp reads in F instead of C but it works fine.

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1985 300D Turbo ~225k
2000 F350 (Powerstroke) 4X4, SWB, CC, SRW, 6spd ~148k
1999 International 4900, DT466e (250hp/660 ft/lbs), Allison MD3060 ~73k