<VV> Brakes HELP

[Ralphsebrell]

1969 Monza
Searching for the reason black dust all over the tire/wheel cover, I found that one of the wheel cylinder  pistons had blown out of the cylinder. ??? 
There is a plate with 2 fingers behind the "pin" (that the shoes and springs go on). The forward piston was able to bypass this "Block". I could not get the rear piston out past the rear "Finger" but I could get it past the front finger.
It appears that that this pin/finger plate & etc can be screwed off of the back plate. Is this so? Can it be removed?  It's on there TIGHT!
This plate/finger appears to be 1/4" thick.
I'm stuck. Any advice will be appreciated.
Ralph