This probably won't help (more likely to muddy the waters), but even all OBS front covers are not the same (and I'm not sure of the year changes they happened):
A deareation valve was inserted in the front cover beginning with engine serial number 201681 through engine serial number 375549.
The front cover was redesigned starting with engine serial number 375549 to help keep the oil pump primed for initial start up.
To accommodate this change, the pump inlet port was rotated 90 degrees which moved the pickup tube from the left to the right.
The front oil cooler header gasket was also redesigned because of the change to the front cover.
The front cover has been modified for the updated reservoir to front cover gasket and passages have been cast and drilled into the front cover to incorporate the standpipe.
The engine serial number that the standpipe was incorporated is 201681.
There was a pretty good thread on PSN on this (I think it may have been Tom S who was a big part of it too). Cheers!