Parking brake cable help??

[meangreen72gmc]

I'm tearing down a 1969 GMC c10 and I'm down to 1 last thing in the firewall before I can take the cab off. How do I get the parking brake cable to pull through the small rectangle hole in the firewall? Its got a clip that holds the cable sleeve to the parking brake pedal frame and that's the part that won't fit through the hole. Or am I supposed to pull the cable from the outside into the cab? Help??