The 400 engine is a "B" engine, (like a 383). A 440 is an "RB" engine.
Only difference is the deck height. 440 RB being a taller deck height. This has nothing to do with pulley depth. However as far as the mount brackets go, you will need to get alternator brackets for a B engine
I've tried swapping these parts before and it won't work. You will either need all the brackets and pulleys from a B engine or the entire set up for a 440. And if it has the 100 amp alternator (which all 400 and 440 Formal's have with a rear window defroster option) it changes all the brackets again.