The 300D injectors will not even fit in your 190D. The last set of injectors I saw from a OM60x engine did not have the same distance below the threads. The OM61x injectors extend past the threads. I would suggest drive the 300D while the 190D is out of commission.

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1991 F250 super-cab 7.3 IDI. (rebuilt by me) Banks Sidewinder turbo, hydroboost brakes, new IP and injectors.
2003 S430 - 107K
1983 300SD - Tanoshii - mostly restored ~400K+.
1983 300SD - Good interior. Engine finally tamed ~250K.
Monark Nozzle Install Video - http://tinyurl.com/ptd2tge