http://www.stagev.com/pages/426hemihead.html
I think they had stopped offering the replacement heads. ???
The Custom heads are a better casting with semi finished dual plugs.
I have a set with standard exhaust port and 2.25 &1.94 valves.
I sent them to Ray Barton to have cnc ‘d.
https://www.raybarton.com/products/stage-v-bare-aluminum-hemi-head