Huge thanks to @Mike_H for his write-up on replacing the factory locker air fitting. These are running $100-125 online these days. Following his instructions, I put together a homemade replacement.
After fighting with and removing the rusted original, the replacement slid right in. The copper tube is line to line and the pressure holds. This is the test fit before adding JB Weld.
I have a set of functioning lockers!
The front line has an air leak somewhere. It locks, but the pump runs every 3 seconds or so. I’ll diagnose that some other day.