I am still working on this. I managed to buy some new valve springs which seem to fit, and I bought some new piston rings that I think will fit. Many of the parts seem to be generic. I bought some new air filter enclosures which were said to have 16mm threads, but the thread is too large for my compressor. You can buy plastic filters with 15mm threads, which might (or might not) fit, but I prefer the metal filter enclosure, so I'm making some adapters with the correct thread on my lathe. We will see how this goes in due course. I bought some gaskets some of which seem to be more or less the right size, but will need a little trimming. The cylinder base gasket was completely wrong (the gasket has 4 screw holes but the cylinder base has only 2 screws). So I will try to cut new gaskets to fit (when the sheet of gasket material that I have ordered arrives). I did buy a cutting compass from Amazon that looks as if it should be good for cutting the larger holes in the gasket. For the small holes I will try to make punches of the right size on the lathe.
So in summary, unless I find something more serious wrong with it, I think this compressor will be restorable, and should then be a good machine. Even if something more serious does show up, I have a second one of these that I can strip for spares if necessary.
Thanks - Rowan