Rochester 1 bbl Carb rebuild (without Power piston rod)

[rwogs]

1972 chevy C10 250 CI engine Rochester 1 Bbl carb (#7042021) M-MMV.

I'm rebuilding the 1 bbl Rochester carb on my Chevy truck. When I opened it up and removed the power piston, there was no rod inside to activate the power piston (#45 on an exploded view of the carb). I thought I may have lost it in disassembly, but when I looked underneath the float bowl, the opening that the Rod for the Power piston would stick through, it was plugged with a rounded, apparently factory installed object/plug. (see pic below) It is a rebuilt carb (I inherited this about 12 years ago from my father-in-law and he bought it used a few years before) but I can't tell who rebuilt it. Has anyone ever run into this? I have another question about a suitable replacement carburetor for this one, but I'll put that in another post.