For 600 hp, yea your best bet is forced induction. I'm not sure how much it would cost to build a NA 600 hp engine but I would assume the price is astronomical. Look at it like this, the GM small block 427 gives you 505 hp at the crank and that thing costs over $16,000. At that price you could supercharge your car, add suspension mods, make well over 600 hp to the wheels, and have a lot of money left over, lol! So for your goals, think blower.
These engines can handle 550-600 hp to the wheels easily. Once you go over 600 hp is where you have to be careful. 650 and you're likely gonna break something. Lots of guys out there claim to be making 700 or even more on a stock bottom end. I do not recommend pushing the block that far unless you have a built engine ready to drop in and you just wanna see what it could handle. So shoot for 600 or less.
Lots of systems out there will get you into the 500s easily for about $7,000. Procharger P1SC will get you in the 550 range with LT headers, ported or FAST IM, and other supporting mods. It can be pushed for more but it seems that around 550 is their limit. The D1SC is a $300 upgrade over the P1SC and it can make much much more. Most people will recommend the D1SC upgrade (if you chose Procharger that is) due to the price. For $300, the D1SC is much better and much more cost efficient than the P1SC. Also there is Vortech, Paxton, and even the LSA/ZL1 blower conversion. Those are the cheaper options. Magnuson, Whipple, KB might cost a bit more. But lots of people who bought those are extremely happy with their choice.
Of course suspension, tires, and clutch upgrades will be necessary to handle all that power. You should even look into upgrading the brakes. One thing I do suggest tho is to not get hung up on numbers. People often have a number in their head on the kind of power they want. 600 might sound like a lot, but if you were to get to about 550 or 575, you'd be making about the same kind of power as the Z06, 13-14 GT500, and Hellcat give or take...to the wheels. Even if you got to 525, that is about 150 more hp to the wheels than a stock SS. And it is nothing to dismiss. That'll get you into the mid to low 11s. And you could always upgrade at a later point for more performance. I'm planning a little frced induction myself next year. And if I can get to about 550 on low boost then that is perfectly fine with me, lol!!