Your spec's on the LT4 crankshaft shows that it is a cast steel crank. I think the LT4 has a FORGED steel crank that is much stronger than the cast poured crank. I will know for sure soon as I plan to replace with a FORGED 383 C.I. crank and rods. Many years ago I has a 1970 LT1 350 that had a FORGED crank( I had it balanced) L.G. Motoer sports in Dallas Tx. is the source of my information on the LT4 crank.
Best Regards, Louis Bartay
1996 LT4 Corvette coupe Tourch red
GM supplied me with a crate LT4 replacement under warranty so I'm using a stock (albeit new) crankshaft which really should be good for up to 500HP. The forged units just give you that much more margin of safety.
If I was stroking the engine or putting juice or a blower on it, I'd want a stronger bottom end but otherwise I think the stock crank is up to the task as long as you keep the RPM's at a reasonable level.