The W block 427 was not sold as a regular option. It was a race only engine, RPO code Z 11. They were mainly intended as drag race engines. The package consisted of the 427 engine, 2 door Impala SS body, aluminum front fenders, battery tray, inner fenders, grille,and the front and rear bumpers. This package was intended to compete with the "Acid dipped" and aluminum nosed Dodges and Plymouths. They are very rare.
The 427 that was used in the Nascar racers was a different block, though it did share a few components such as the crankshaft. This is the "Mystery Motor", though GM called it the Mk.2. To my knowlege, neither engine saw use in trucks, they were race engines only.
