Yes, the firewall would have been painted the same color as the exterior.
Another spot to check is the back of the cab that's covered by the front panel of the pickup bed. Most times a repaint doesn't bother to remove the bed and paint the rear of the cab and front bed panel. Also, where the side view mirror bracket bolts to the cowl is a good spot to find unweathered original paint.


Kevin
1951 Chevy 3100 work truck
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1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.