It's normal. The engine is offset to clear the steering box.
The 455 and 400 blocks are extrnally identical as far as size and fit are concerned. As long as the 455 has the right two motor mount holes drilled and tapped - or all 5 for that matter - you will have no problems setting either the 400 or 455 in there. It will look just like that, either way. Use the right mounts for a 400 Firebird from 67-69. Don't use the later 455 mounts from a Firebird. They won't work.
