i gotta go look again, but im pretty sure there is a difference with the exhaust manifold as well, and its location on the block, but im not 100% sure. plus, the valve cover looks a lot cooler than the old 4g63 valve cover.
edit...
yeah, the exhaust manifold would be on the wrong part of the block if im not mistaken... look at this picture.
even though the exahust manifold is in the same part of the engine bay on the eclipse, the orientation of the evo 8 block would make it quite a job, if not impossible to swap into an eclipse. oh, the bottom end on the evo 8 motor is also all forged, i think, but im not 100% sure about that, ill do some reasearch and let you know.