I wanted to keep my original handle on my 57 also. I removed the entire parking brake setup, except the handle and got all new cables and everything else I needed from Control Cables (
www.controlcables.com). The only fabrication required was to make a small bracket where the cable comes through the firewall and another one to connect the cable to the handle. It's not difficult and CC folks are friendly to work with. I spent about $175 total with shipping.