Firewall Wiring Harness Grommet is critical! If your wiring should chafe inside an unprotected firewall hole, the insulation will be worn away, causing short circuits and even electrical fires. Prevent tragedies like this by maintaining these important parts! Installs on the driver side of the firewall and the connection for the underdash wiring and the under hood (headlight/generator) harness is made here. #353 will work on any 1956-57 Chevy model.