[jwd]

Everything I've read says they went with the 428 because the 427 was hard to get and the 428 was $410 cheaper. Since they were losing approx. $1000 per car, it made sense to go with the cheaper motor. There were a few 427's installed after the change but most were 428's. Supposedly, the brochures were changed to 428 specs. but it wasn't advertised.
Most agree that the 427 signifies the body type, not the motor.