The old 289/.690" Comp is no slouch, easy on parts, and can make very good power.
We've seen 849hp 753 Trq using it on a 540 with ported INDY "SR" heads, which granted have a better Exh than the EZ Head, nonetheless, pretty forgiving old grind.
https://www.youtube.com/watch?v=VzWhkC4dAI0

We've moved on to a newer SF750 Bench nowadays, so no point going over "where" we had the SR's on the old Bench(they took us some time), but I suspect not that much better than your EZ's.

Better to be a "has been" than a "never was".