It was pretty close to ten years ago that I received the 400-3. My recollection is that the runners were uneven and ragged at the head face.
Don't know if this helps........but...........
I just went out and measured the RPM heads we were using on that engine and we had ported the heads and intake manifold out to 1-1/4" wide and 2-5/8" tall. The intake manifold face of the runners were definitely smaller than that when we stared.
Maybe call Indy.