Ecoboost - Heavy Duty Trucks

I see the 3.5 Liter EcoBoost is rated for 420 ft-lb of torque and is supposed to get fairly impressive fuel economy. Has anyone considered the effects of scaling one of these up to the 12-15 liter size commonly used in heavy-duty trucks? The typical fleet truck produces between 370-450 HP with 1500 lb-ft of torque and gets in the neighborhood of 6 MPG with a full load, running 13 liter turbo-diesel straight 6 engines.
With recent emissions regulations targetting all diesels, requiring Urea/DEF and DPF filters, I think the idea of a heavy duty ecoboost engine makes a lot of sense. It could be produced at a far cheaper cost, and as long as it got the same fuel economy and reliability, it would be a very popular engine - especially since it would have reduced maintenance and lower per mile cost without having a DPF filter or DEF injection system.
Ford would have to produce heavy-duty trucks again for this one - everyone makes their own engines now, not like it was in the 1990's when you could get any engine in any truck.
Kyle 03/14/2011
An interesting idea, but I don't think it will work. The HP and torque curves of gasoline engines are very close together, and starting around 450HP, the torque curve tends to fall below the rated HP. With the EcoBoost this might not be true, but I wouldn't expect the torque to exceed 600 FT-LBS at 450HP. you would need around 1200 HP to get 950 FT-LBS.
the reason diesel gets more torque is because it contains a larger percentage of crude oil, which gives it more power per gallon of fuel, and in turn uses less to make more. Gasoline is a completely different chemical mixture. No matter what you try, you can't replicate diesel performance with a gas engine. It's just not possible.