Think trying to drop a 1st gen body on a 3rd gen frame would stand the best chance of success.
Even then, things like a/c, brakes, steering and the radiator are going to be sorely pressed for space.
Compared to any engine Ford ever installed in the 1st gens, the 4.6 is huge, nearly double the width and half again as long as the 4.0 ohv V6.