E-street vs Promaxx vs 440 Source

I would go with all except source having the same casting. Freeze plug, straight spark plug etc. probably close but not exact.Swingn’……

Exactly.
The Stealth Head is it’s own casting, although the basic port configuration is very similar to the others(i.e. another copy of the RPM heads).
Compared to the other import castings, I actually prefer the port openings of the Stealths on both intake and exhaust.
It’s not a big thing either way......but they aren’t the same.