You can install the battery cable without going through the firewall. You can run the cabe through a hole by the fusebox. This hole leads outside the doorwhere the wires for your windows and power locks are. When you get there you can take the covering off he iside of the wheelwell and there is a hold that youcan feed the wire through to the engine compartment. If you can find the way it makes it a lot easier than driliing through the firewall. If I can do it im sre you can.