One thing I learned when I did the 400 to 440 swap was that all of the brackets I had on my 400 did not work on the 440.
The 400 (and 383) are short deck motors, and the 440 is a tall deck. So, when you go looking for brackets, ask for 383 or 400 brackets, not only "big block" brackets.
I originally wanted to keep my AC, and wasn't able to. Not having the AC meant I had to swap all of the other brackets, and even had to use a different power steering pump. It was a cascading effect. Try and get them all at once, from a 383 or 400, all from the same year.
Cheers,
Covert