500 flywheel HP is not an easy feat to achieve especially since there is so little scope for raising the RPM limit. Already with 8600rpm we achieve a bit more 'peak HP'
We can all see that it is quite possible to get to around + approx 40-50 hp taking the car to around 450 crank HP. Realistically without the marketing. Maybe 460 in some cases.
Now we are looking for another 40-50hp. This will require some serious work to the heads, some massive cams and then you have the driveability issues below 3500rpm.
Most likely to get to a real 500hp you will need to stroke. If you want some reliability.
It is way way easier to have 500 genuine HP with a real nice supercharger setup. Something that currently doesn't exist on the market. A 500hp intercooled kit would use really minimal boost and therefore produce really nice consistent power even on the track. This is way way cheaper than trying to get 500hp from NA.
390 SAE whp is really about the best we are seeing and that's not on every dynojet either. This is not even close to a real 500 crank HP yet. You would need on a dynojet 430-440 whp to make a genuine 500 crank HP. That fits exactly in what I am suggesting what the extra is needed - +40-50 whp.
Remember, V10 M5 makes an easy 430-440 whp on the same machines stock and that is a genuine 500 hp engine.