73-87 C-10 Firewall support brace1973 1987 C 10 Firewall support brace. If you choose not to reuse the original bracket when shaving the firewall on a 73 87 truck this brace is necessary to add the strength and support back into the firewall to eliminate flex on the master cylinder. A single layer of 18 gauge is not enough and will result in spongy pedal feel or poor braking performance. Designed to be used with our firewall panels but will work with other manufacturers as well.