Are you bloody serious.
Dude you're on crack!
How the hell will you fit the 5.0L in the Contour engine bay sideways AND mate up a MTX-75 tranny to it? Plus, a iron block engine like the 5.0L weighs a ton, compared to the Duratec which would make the car handle like a shrimp boat if
somehow you got this brainfart of yours to work!
I doubt you ever even seen a 5.0, because if you did, you'd realise that what your suggesting is totally ludicrous.
PS - what's a "Roush prepped" MTX75 - I've never heard of it - did they make those from Unobtainium?