Paul, it's been a while since it was posted on pro-touring.com but others have made a simple 'z-bar' bracket that bolted to the inside of the firewall and kept the rod from every falling out. Looked quite simple to fab and was effective. The rod passed through a hole in the bracket.
69 RS Conv therapy program, Autogear M22, 8-pt cage, with a new 410! SOLD
New therapy program - 68 Coupe. Will be survivor exterior, modern underpinnings! SOLD
67 Belair with perfect floors, pinchwelds and firewall. Hmmm!