Stock Stroke Versus Stroker Combo !

Actually the Eagle cast were bad for big horsepower. Scat cast were the ones Mopar badged and sold as there own, and I know of serval surpassing 600hp NA, with nitrous on top of that and they've lived just fine. But - cast cranks need Mallory to internally balance and that's what you want. The difference between good cast crank cost and the forged cranks is probably less than $200 when you include the cost of the Mallory.
The difference between 3.31" stroke and 500hp and 4" 500hp is only the rom and the matching torque curve. The 340 will be nasty - rough idle, high rpm, needing gear and convertor... The 416 will do it with a moderate idle and run as fast with 3.23s as that 340 with 4.30s. Money wise the 4" is 30-40% more cash outlay. Sonic test the block.