Keep the cast one. I believe the vanes are taller, and the gap less between the plates. If you recall I installed a new one and had issues...yada yada yada...I went with the GM cast style, and filed the vanes until they cleared the plates. I have a nice tight fit..Jee I like the sound of that...ok back to the subject...I think the stamped one will or could be more prone to less efficiency with a larger gap, thus allowing more coolant to bypass the radiator? Your 428 may run hotter than the 400 if your build it up, I would keep the cast one as my vote.
