The stock tool post for the Mcnaughton coring system is too short for the G0766 Their web-site mentions a longer tool-post, but no one in the US appears to stock it.
Did you bore out your banjo hole to 1 inch, Ralph? If not, it might be a bit harder to find a 25mm replacement post for your McNaughton system. My Woodcut system came with a 6" long post, which was plenty for the G0766 to raise it to cutting height.
I used to turn on a 9" lathe and then bought a Griz G0766 22" lathe. I had some curved tool posts that I liked from the old lathe and wanted to use on the new one. But they were about 6-1/2 inches too short and had a 7/8" tool post. So I made an adapter. It is a length of 1" steel (that sits in my Griz banjo) followed by a ~2" collar (about 2" in diameter) at the top. I machined the collar and the 1" rod to be a close fit pocket. Then I tapped a 1/4-20 or 5/16-18 (or something) hole in the collar for a set screw. I silver soldered the collar to the 1" rod. All of the forces are in compression, so the part is practically indestructible. I suppose that a 1" ID coupling with a pair of set screws and no silver solder would also work. If you have access to a metal lathe or a friend with one, it shouldn't be all that hard to make an extension adapter.
I had two other thoughts: 1. Email Kel McNaughton and ask him how/where you can buy the longer tool post that he mentions on his website (like the one for the Powermatic) 2. Go to a machine shop and bring along your regular (short) tool post and have them quote on fabricating a new longer one. The features on the tool post seem pretty simple so it should not be terribly expensive. If you have a friend with a metal lathe, he or she could also do this.
