If you're not sticking to Ford...A Mitsubishi Eclipse GST or GSX would make the 5.0L obsolete... mine averages 22mpg for a mixed commute and gets ~27 mpg on the freeway. It's making around 270 flywheel hp right now with unrestrictive intake and a slightly bigger turbo. It also sticks to the road like no Mustang I've ever driven. Basically an all around fun car with reasonable gas mileage.
Hello Mc Fly
If he/she wants something that can haul but and be a good alternate to a SVT 24v V6 contour... ummm I got a idea why not a 2.3T
It gets great mpg and stock depending on what year/car you get it from does 140-210hp 