I did some more work and realized that the bulb holder is adjusted with a screw from the back of the shell and there is a coil spring to keep the screw in tension. There is also
Bratton's p/n 17870 "The steel ring on edge of headlight bucket. Your reflector sets and clips to this ring. Have your welder spot weld these in place." I don't have any of that. These parts also seem to provide the ground path for the lighting circuit.
I have purchased some hardware store screws and springs to get me going. The parts store don't seem to list the screw and spring. Are there any other good sources? A swap meet should work.
Can anyone measure the length of their spring and screw, so I can trim to the right length?
The method of compressing the spring and getting the screw into the hole in the bulb holder isn't obvious to me. Any tips?