The top speed of a 1967 Pontiac Firebird varied significantly depending on the engine option. There's no single answer. A base model with a smaller engine would have a much lower top speed than one equipped with the high-performance 400 cubic inch V8. Factory figures weren't always published for top speed, and even if they were, real-world speeds would depend on conditions and driver skill.
Therefore, it's impossible to give a definitive answer without specifying the exact engine and options of the particular 1967 Firebird.
