i have C.R.S. question

[millmaster65]

I'm in the process of changing out a heater core in 85 K10 Sub.
This is a dumb question on my part because I've had it out before.
Heater box is out of the truck but I am having a case of CRS.
Do I have to punch out Rod/pin to remove the core from the box??
Is there a trick or technique to it so I dont break any plastic?
I have all screws out already.. even the hidden two.

[beastie_3]

My 79 has pressure tabs keeping the core in place. Two screws for each pressure tab.

[millmaster65]

yeah, mine has metal straps held by screws. but, i cannot get the back cover separated from the heater/ac box to gain access to the core.
there is a metal rod goin through the outer and inner heater box that diverts air and i think this needs to be removed somehow but I don't want to destroy anything.