I like the torque bump from the increased ignition timing. Nice gains from just 50/50. These were ideal conditions with low humidity and temps in the 60s. Gains relative to a stock car would be greater with temps in the 90s, when the heat takes a greater toll on power given the timing due toengine compression and available octane.
I am not sure what the SAE corrected results would be, though they could be calculated. They would certainly be less, maybe even dropping you to 390 rwhp. That would still be very good for the relatively few mods. Most cars seem to need all the bolt on mods (x-pipe, filter and/or intake, pulley and tune) to get to or break 390 rwhp.