Hi Jeb,
I can't see a problem with the V10 making those sort of numbers without a blower. We have some hot production cars with an aussie version of the 5.4 motor that make nearly 400HP off the showroom floor in a mild state of tune. A significant increase in capacity to 7 litres should be able to produce the power they've quoted without a blower.
This is the new Ford BA Falcon GT
http://www.fordperformancevehicles.c...?link_id=2.161
The new Holden (GM Australia) Monaro HRT427 is quoted as making 560HP out of 427 cubic inches naturally aspirated. You will be getting the less muscular little brother to this car soon (but badged as the new Pontiac GTO in the US). This is emissions legal in Australia too and we have some tough emissions laws.
http://www.ultimatecarpage.com/frame...ar.mv&num=1488
http://www.hsv.com.au/main.html
Hot family sedans are very popular down here and only recently has Holden started making a coupe again. Maybe the marketing guys in the US are trying to encourage some of that trend over there?
Cheers