The 2.8i supplement manual lists one torque for oil cooler related parts and that is the "Threaded sleeve - oil cooler" which is 20-40Nm.
This is the sleeve that passes through the oil cooler body and holds it to the threaded bush screwed into the block.
There's no other torque specified, and indeed on the reprinted supplement I have it shows the oil filter spinning direct onto the oil cooler, with no L shaped hanger. The nut that holds the hanger on probably just needs to be as tight as an oil filter would be because its only a rubber seal in there, so just normal spanner tight.
I found last time I changed the filter that the hanger can rotate forward/back when you are encouraging the old filter off so its not rock-solid tight.
If that makes sense.
I don't know when the extension was added, my 1983 car has the extension must have been a relatively early revision.