The VIN only tells you if it was a V8 or a 6 originally. Unfortunately, there is no way just looking at the car to tell exactly what engine it was built with.
A 5/16" fuel line from the tank to the front tells you it was a 6 cyl or a 283, a 3/8" line says 327 or larger. That's one way to narrow it down a bit at least.
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars (now converted to a "factory" 4 speed)