I believe an evo3 radiator is a direct fit, but hopefully a search on this board will reveal the true answer. I know user Bimmubishi posted about this exact topic several years ago. The only difference, from what I recall, was that the evo 3 radiator doesn't have the temperature bung installed in the lower part of the radiator.
I've been eyeing different radiators on ebay, and have seen that you can get full aluminum ones for around $150 shipped. I can't speak for their quality or effectiveness, though.