thinkin of swapping in a sb 400

[nu2u72]

hey guys, my truck (72` gmc ) has a late 70`s 350 in it right now which is nothing like the older motors power wise, so I`m thinking of swapping in a nicely rebuilt 400. Now just so you know I used to work in a engine shop where we built anything from stock to wild but that was many moons ago when I was 17 ( now 36 ) so I know how to rebuild an engine.
My question is. I`ve found a 400 2 bolt block here locally for a good price, so what do I need for a crank for this bad boy? does it have to be a 400 crank or will a 350 crank work? I`m not familiar with the 400 at all but know the 350 in and out. I know you can put any 350 head on it but you have to drill the steam holes, and i know the intake from any sbc will work.
I guess what i`m askin is what exactly do i need to look for to rebuil this motor? 6" rods or 5.7" rods? I`d like some power, like in the 350 to 400 hp range any of you guys build such a thing? I know it would be much easier to just find a whole 400 but they are not easy to come by around here.

help