http://www.autoparts.com.au
I put it "out there" for a replacement full instrument cluster for my 1982 tourning wagon

The result was two replies with the clusters being available and I also picked up another oil gauge sender unit as a spare. While I have the original Subaru part number for the sender they are no longer available from Subaru (so I believe).
The best bit is the new cluster has 146 thousand ks on the clock and mine has 255 thousand ks. This (hopefully) means it has had less use and should last another 29 years (I dont think it has been around the clock)
If it is OK for the form and anyone is interested I an happy to recommend the two suppliers who replied. Obviously one was the end supplier.