2cents
This is an interesting thread. I will chime in.
Turbo + 5.0 is pretty awsome. Its also a lot more work and headache then many make it sound like.
To me, there are a few parts to the equation when talking about power and MPG. You have a light car, so thats a plus. As mentioned earlier, a really "economic" gear ratio is a pretty big factor. Altering the OD in your auto is probably difficult, but altering the rear end isnt. So, put a low gear in the back, like some 2.73 or something.
ONOZ!! Someone will say, because thats taboo when talking about going fast right? Maybe, but consider... your car is really light, and you arent talking about a drag radial trailor queen car. How do you make 2.73 fast? Huge power, or better yet, huge ft/lb.
So what makes huge ft/lb? A 5.0 with a kenne bell. In fact depending on your set up it can make so much power you will have traction issues during normal driving.
I just thought I would throw that out there. I mean a kenne bell is one of the easiest/least intrusive set ups you can do on a 5.0. The power is there right away, and can overcome the negatives of a low rear end to a point. If you keep out of the boost(under about 2600-2800 rpm- easier with a low rear end) you should see mid twenties easy for mpg, more with a good tune.
There is one consideration though, KB doesnt make a blower inlet for anything but stock 5.0 GT or cobra manifolds. So aftermarket lower intakes dont work. On the plus side, a gt40 lower from an explorer is like 40 dollars on ebay. It will work plenty well enough. If you do the rebuild on the engine and put in a stout bottom end, all you will need is bigger injectors and a pully to make even more power( and a tune)