I'm running a scat cast steel 3.40 crankshaft. Its plenty for my stock block combo. Forged cranks in a stock block do nothing but waste money and add weight to the rotating assembly.
if you are running spray (over 150 hp) or forced induction, I'd suggest going with Forged. These days a cast crank will be under 200 bucks, and a forged about 400, but after all the other parts, it adds up.
With me, i am planning a stroker build up this year. Either a 302 to 331, or a 351 to 393. Either way, I'll be using a cast steel crank, forged rods, and hyper pistons. I'll also be using a set of budget priced aluminum 225 heads from a supplier on ebay, where they are about 890 a set. I'll shoot for 10:5 to 1 compression, at most 11:0 to 1, and will run fuel injection. Then I will spend a little extra to get a cam cut to where I need it. If I go with the 331, I'll be looking for a safe 450 hp. The 393 and I'll want a safe 500. Safe = daily drivable (even tho I drive my cars under 10k a year) I want something that won't need a rebuild every year.
And it's fine to me if I need to run a vacuum cannister, and a high output alternator. But that all depends on the cam.
Im building a stock block NA 331. i chose a nodular iron cast crank. just make sure if your buyng new it has been magnafulxed, sonic tested, shot peened, nitrated, heat tread...all that good stuff. i dont plan on much more than 425 horse at the crank.