500 whp na isn't that hard to do. It's just hard to do and keep it streetable on pump gas. The easiest way would be a 351w. Well, actually a stroked 351w would be easiest. But there's nothing cheap about it. If you are 100% sure you'll be staying na, you can save some money by using hypereutectic pistons instead of forged. But most of your money will be in the heads, anyway. You'll have to spend some money there. You'll also find that you'll be spending a lot on supporting mods. A strong 5 speed manual transmission will cost a lot. If you want a 4 speed toploader, that would hold up, but the bellhousing and shifter will cost another $800-1000. An auto transmission (c4 or aod) built to hold the power are the cheapest options.
Whatever route you take, if you have the time to shop around, you can usually find everything you need on the used market... even if you're looking for new parts. But I would consider building the motor instead of buying a crate motor, if you're on a budget. From what I have seen, you pay a premium for convenience when you buy crate motors. And sometimes, you end up changing parts on them anyway. I figure you're better off finding a GOOD (I can't stress that enough) machine shop or individual to build you one. I usually opt for having them assemble the short block and then I finish it myself. You can save some money assembling the rotating parts yourself, and I've done that too, but for warranty purposes on an expensive motor, it could pay off in the long run to have the pros do it.
