Thanks for the comments!

Worked on the gauge panel again today, got the rings welded up...








Then to tip a flange to hold the gauge in place, used these in the bead roller....





Applied a bit of pressure and started tipping the ring gradually as we went....








After getting the initial flange tipped to almost 45 degrees, the body hammer was used to get the flange to 90.








Fitted, and shown with the gauge's mouting bracket in place.....











Now to fit the rings to the panel....











....and fine tuned with a drum sander.. A view in the panel....








Rather than weld around the perimeter of the hole, which will surely warp things up nicely, I'll tip a flange on the underside of the rings and spot weld to the panel.