I figured the pushrod had to be keyed to the ferrule. But I would have never thought that the ferrule was threaded in.

Dudley:
Yes. This is why it has notches -- really the very outer ends of a screw slot. There is only about .25 inches of fine thread. When the ferrule stops unscrewing upward, it's time to tap it out from the bottom.

Best, Kensal

Got it out no problem. I found that a bit in my Magna-tip thin bit set from Brownells fit perfectly.
Bit #270-2
Width: .270 (6.8mm)
.025 thick.