On the front driver side of the 300sd engine in the head is a plug that goes into the timing chain area. I used this plug to return oil into the engine on a 240d that i had and it worked fine. I drilled and brazed a fitting that i needed. The only problem is finding where to get oil under pressure so i can tap in with a "t" so i can also install a filter. The sending unit would be the best place to get the oil. As you said where to get the fittings and what size?
94 dodge cummings,86 ford 6.9,75 mbz 240d[ sold], 82 mbz 300sd,83 mbz 300sd