Out of my 4 heads, there were:
- 2 hollow brass plugs (solid hex head),
- 1 solid steel plug (square head), and
- 1 steel/alloy solid plug (indented hex head).

Yes, the easy-out process is a crap shoot. The brass could not "rust weld" to the head, so I guess that made the removal easier.

I am still slowly working on the torque-tube and ball/bell. I think I am about half way there - I want to remove no more material than necessary to allow the bell to slide back, yet still provide a tight fit of the bell to the tube.