Now that's an interesting question. Even though the 455 is a tall block maybe one of the members with Olds engine experience can shed light.
While you are awaiting more feedback, here's a YouTube feature on Old's 455 swaps into 2nd Gen F-Bodies. If you read down into the comments, there's talk of using 68-76 Cutlass 455 headers and 403 engine mounts. I know this feature is old but maybe if you reach out to the author or some of the folks commenting, you might get some info from them if they're still monitoring the thread. You could always search for more 455 Old's swaps on YouTube. Good Luck!