I wonder if it would be possible to fish a nut or bolt in there with a pair of long needle-nose pliers, 'magnet on a pole', or somesuch. Probably easier said than done. Also probably easier with no spring in the way, and the CA sitting on a bench.
I would probably consider drilling a strategic access hole if I did not have a welder, but I really hesitate to recommend that to anyone online for fear of how or where it would be done.
Welding is probably the easy answer. You could certainly avoid removing the CA with a weld. The strength of this weld is not super-critical. It takes only half the load, and the tiny (6mm?) studs are a good indicator that the load is not that great.
Even if you do not have a welder, I find that welding shops charge very reasonable rates for small jobs in my area.
1986 300E 5-Speed 240k mi.