6U D4 rear main cap

I have a D4 6U18?? the rear main cap may have something missing.
There is a threaded hole in the center towards the rear of the main cap. It is drilled to the crankshaft. My guess is that it is used for an anchor to pull the cap. I also guess that it does not have a plug and the hole is to drain the oil at the rear main seal. I am trying to assemble a pile of parts.

Hi Cat60,
the hole you mention is there to return the oil picked up by the rear main oil control return screw thread/scroll machined into the crank.
The rear main bearing has a groove machined into it to collect this return oil and dump it down the drilling to the sump.
The rear main oil sealing is done by the scroll only on these engines. There is no positive rear main oil seal like later engines with a lip seal or similar.
The grooves at each side of the rear main cap are to be packed with packing rope to seal the cap to the cylinder block, this stops oil seepage out into the flywheel housing.
The packing is Cat P# 2B2414.
Scan below shows how I was taught to pack the packing in a zig zag fashion whilst tamping the packing in one zig or zag at a time, to get it nice and compacted to seal effectively.,
Had a home made "D" shaped punch to do the job.
Hope this helps.
Cheers,
Eddie B.