Throttle cable removal question

[cox71]

I need to remove the throttle cable from a 71 to use on another truck. I have been tring to see how to take it out with out damaging the cable.
It looks like there is a plastic nut on the firewall side. I tried to turn it but when it did not come lose easily I stoped before I ruined it.
It looks like you need to disconect the cable from the pedal, then losen this nut, then I guess maybe you depress some ears on the square end inside the truck and remove it out the firewall side? Any help would be appreciated. Thanks