Fighting with the far end of a spring is not the most relaxing way to spend a Saturday morning, but it was necessary. No success as of lunch time but lots of sweat expended. The spring is made from stiff wire, which keeps the hook ends tightly circled and in place.
If there were no obstructions, the spring would be held at about a 75 degree angle to the interposer, the opening in the spring hook end slid over the interposer and then the spring swung to 0 degrees to force the end of the hook through the hole in the interposer.
However, the maximum angle for the spring end, given the constrained environment, is about 10 degrees, far too little to allow the usual method of attachment. I have just about enough room for the spring to enter the space within which is the interposer and its hole.
With strong lights and just the right orientation, I can barely make out the hole in the interposer into which the spring will fit, but am finding it almost impossible to manipulate the spring enough to matter.
I posted a request for ideas from the golfballtypewriters group which includes quite a few service people who worked on these machines. Perhaps there is a trick or an access direction that isn't apparent to me.
This is probably a task that will burn many hours until somehow it clicks into place and I begin putting it all back together.