Cavebull,
I wasn't aware there were any long running safety concerns with running a wire through the firewall. On the trucks I have seen, there is a rubber grommet that adds protection to the large, well bundled and insulated run of wires that penetrates the firewall.
The wires are quite rigid and it seems like it would take a terrific amount of constant wiggling to cause them to short against the metal of the firewall.
Stuart
