If I had the money to put a Hemi in my 69 Cuda, I'd find a 426 Hemi. It does fit. There was an article in a Mopar Muscle about 20 ago where a man installed a 426 in an A Body. He did it such that the hood closed.
Can you imagine taking a 69 Barracuda to a car show and popping the hood to expose a dual carb 426 Hemi?