If the tag on the frame and the stamp on the engine are the same numbers, is that not a numbers matching car? The engines and frames were made at the different places, but a matching plate was included with each block to be attached to the frame during assembly. I've also heard the firewalls were the same color as the car. GM painted the firewall and underside a dark brown, then painted the entire body afterwards. Did they paint the chassis the body color too. No. They're weren't hot rods.