Maximum bore
427 truck block is good to 4.350" to 4.375" maybe. I would fill it to water pump holes for that big. But you can use a 4.375" stroke or possibly 4.500" stroke on tall deck to get maximum cubes, depending on rod length. This would take cubes from 505 to 540 range.
It has to be a siamesed bore block to go above this size which is a Bowtie GM block or Dart, etc.
Remember, a tall deck block and aftermarket heads create issues with headers fitting in any stock frame car.
That being said, a tall deck or short deck 496 is just a small bore 540 and will do a very good imitation of one if the combo is correct.