Here's a list of 300Ds on BaT, the few that I looked at had nice pix of the engine bay which may help.

mercedes 300d For Sale - BaT Auctions

__________________
Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC