60-66 C-10 Firewall support brace60 66 C10 Firewall support brace. If you choose not to reuse the original bracket when shaving the firewall in a 60 66 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. Precision