If you're doing a 331, you have to fit it in an 8.2" deck height. half of the stroke + rod length + compression height = deck height. You won't get pistons smaller than 1" CH, as there needs to be space for rings, and you don't really want the wrist pin invading oil ring territory.
so 8.2 - 1.625 - 1 = 5.575 means you'll need rods shorter than 5.5" approximately. Also, longer rods are weaker inherently, as a trait of length.
Which gives you 5.4" rods, for a nice number, and a bit more room for the CH of the pistons, so the rings don't have to be so far up, which can weaken the crown.
That's the observations I've made. They may not be correct, in fact, if not, I'd like someone to say so, and why.