What is the difference between a Chevy 400 and a Chevy 350?

The bore and stroke is different, But if you set the 2 side by side they will look the same other then some 400 engines have an extra freeze out plug in the side of the block that the 350 don't have.

350 bore and stroke is 4.000 bore,stroke is 3.480

400 bore is 4.125 and stroke is 3.750