[SPF2245]

Well, based off the point of this thread. I'd use a modern Chevy LS7 powerplant, which is to say, it currently meets all the emissions standards and I'd believe in a cobra with the correct gearing would/could get close to 30+MPG on the highway (55MPH) with the correct programming. I believe we'll soon see the "power" button become a standard on performance based vehicles along with a "economy" button under which changes tuning, numbers of cyl.'s used and such to make the feds and states happy. The current 5.7 hemi uses the cyl. deactivation, that mixed with some leaning of the running cyl. even more could improve milage.
And all the while still making all the good noises...the new LS7 sounds GREAT at WOT.

-Dan