The Stage 6 are a greta head but I have never done a dyno test with both the EZ & 6 to see which is better , the EZ is easier to get & does Not require external oil lines , the 440-1 Indys did & the oiling had to be restricted or it flooded the heads with oil , the cam fed pulse system is better , the Indys do need to offset rocker though & you can get the EX with max wedge port size .
What are you thinking ? you have the Stage 6 heads , not going to use them ?