OER Parts offers a wide selection of Body Panels for your 1978 GMC All Models. OER Parts offers 1978 GMC All Models Full Firewall, 1978 GMC All Models Partial Firewall 1978 GMC All Models Firewall Body Mount Patch Panels, 1978 GMC All Models Firewall To Floor Braces, 1978 GMC All Models Firewall Extension, and 1978 GMC All Models Firewall Delete Plate.