OER Parts offers a wide selection of Body Panels for your 1974 GMC All Models. OER Parts offers 1974 GMC All Models Full Firewall, 1974 GMC All Models Partial Firewall 1974 GMC All Models Firewall Body Mount Patch Panels, 1974 GMC All Models Firewall To Floor Braces, 1974 GMC All Models Firewall Extension, and 1974 GMC All Models Firewall Delete Plate.