it is quite subtle, but for a 56 I would get the vintage stagger (this comes in 2 styles, 54 and vintag. The vintage stagger makes the top E & B lowest, then the bottom E & A, with the D & G tallest. The 54 has the G magnet lower and A higher.
I like the 54 stagger on my apaches. I think the sound with them is very even. I have them in a 57 strat.