Firewall Difference Between AC and Non AC for 1968
Short answer: The firewall holes are different sizes — the A/C opening is about 6″ wide × 11″ tall (narrow and tall), while the heater-only opening is about 14″ wide × 5″ tall (short and wide). So a non-A/C heater box won’t simply bolt onto a former A/C car.
You can adapt it: cover the original A/C hole with a piece of sheet metal (silicone and pop rivets), cut a new hole the shape the heater box needs, drill a couple of mounting holes, and repaint the firewall. Note the heater controls are also different on non-A/C cars.
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Content last modified: June 13, 2026 at 10:06 am
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