As Dave mentioned, you have the wrong cable... Also, when working on your parking brake cable, make sure your brake shoes are working correctly. I assume you have a stock truck with huck style brakes? There's a concentric bolt (spelling?) that holds the parking brake arm on the shoe. That's an adjustment also. For the shoes, make sure they are all moving freely on the pins. When I did my brakes, I used anti sieze on the pins. The service manual (available on line) has good instructions.

David Gilmore
Stovebolt Pictures
Paint progress
____________________________
1950 Chevy 3600