Magnum shortblock capability.

What is the goal, or what is the plan for the car, along with weight, transmission, etc.?
The stock crank and rods can live a good long life at 400 horsepower, which is doable with a piston swap for compression, and a good camshaft and intake choice.
If you are thinking of keeping the stock heads, consider the cost involved in rebuilding those heads. Otherwise, you'll be losing a decent amount of power.
If you keep the camshaft hydraulic, you don't really need to worry about the crank and rods too much, unless you add a bunch of nitrous.
Do some google searches for the project sledgehammer 5.9 engine that IMM built up. Plenty of power, but he did use his prepped EQ heads.