This post seems to come up now and then. There are 2 ways (that I know of) to open up the gauges. Either cut the ring or pry around the underside of the ring to open it.
The replies seem to be 50-50 on which method is the best. I have only tried the "cut ring, JB weld and clamp" . The other way of doing it seems to me that you would have some disfigurations after resealing the rings, and potential rust on the areas where the screwdriver pry's it open. Has anyone tried both ways of doing it?. I like the idea of not having to cut them, but I'm afraid to venture into the unknown on my 71 gauges.