His 87 engine is the donor and I am assuming that he has all the required sensors intact on the donor engine. The donor's IP should be equipped with the sensor and actuator.

If he's not running A/C then he can probably get away with using none of the controls and just dial the IP to a decent idle speed.

The only downside to that approach I can see is that the EDS computer derives the tach signal. He will need at the minimum the OVP, EDS controller and ring gear sensor for a functional tach.

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The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech