Engine Quest Dodge Magnum Heads New Zealand castings.

To give you a little bump.....

I'm no expert with Magnums, but i believe the NZ castings were superior before they moved to China. That said, if i recall, the intake ports were in the 170ish range. Not sure what your goals are, but 400hp with a 360 is easily available. Now 500 would take some compression and a big cam, meaning not streetable for most. As far as a stroked SB, i'd use them to build huge torque in the 3k to 4.5k range and let the HP fall where it may. I have seen where the big intake valve really likes a good bowl blend on those.

With all that...lol...Good luck with your project and i'm sure you'll get a lot of different opinions.