Can it be done? Sure, but it is going to be very expensive and time consuming to do it right. Here is a thread where someone did the body conversion the propper way:
http://www.r3vlimited.com/board/showthread.php?t=196500
And while I understand the desire to have the e30 M3 look, maybe something along the lines of a euro bumper conversion would make sense, that way if you son changes his mind back to wanting an F150 you have not thrown tons of money at a project you cannot sell.
Euro bumpers can be seen on this car:
http://bringatrailer.com/2009/05/12/rare-in-the-usa-1985-alpina-b6/