I KNOW this is not a "Space Enhanced" task.
[You might have to use the OLD Beam type Wrench]

EDIT! [Ignore my previous suggestions]

(Dagnabitt!)

The Fuel Pre-Heater Heat Exchanger's Metal Fuel lines WRAP around the Oil Filter Housing
ON TOP OF THE Oil Pressure Sensor making access by normal
humans Nigh Impossible!
(I can "SEE" the German Engineer Laughing as he tells his grandchildren how
they eliminated another DIY avenue.)

I'd remove the Fuel Pre-Heater's H.E. and CAREFULLY cut back the Metal lines
(The difference to be made up of Rubber/Viton Lines.)
[Heck,if I can get one of those Mini-Tubing cutters in there,that'll do the job
and allow the H.E. to stay in place...It Looks like a FUN job to R+R also.]

If you do remove the H.E. from the head a new "Sealing" o-ring would be a
good idea. Pn 012 997 51 48

call out # 233 is the H.E.
#245 is the Seal Ring.

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'84 300SD sold
124.128