The 454 will be a much newer engine that the original-equipment one. The 55-57 models would have had either a 265 cubic inch V-8, or possibly a 235 or 261 cubic inch 6-cylinder. It's probably been repowered with later-model running gear, at least the engine. A 454 would bolt onto an original V-8 bellhousing and work with the SM-420 4 speed transmission, but it will have a lot more horsepower and torque than original. There would have to be some pretty serious modification of the front engine mounts, radiator, and possibly the steering gear mounting and linkage to make the 454 work right. Inspect the conversion job carefully to see how safely and professionally the engine swap was done.
Jerry
