I'm not a big truster of what they say on their write-ups... Remember they had the intake valve wrong for years and I think they may have just corrected that...
I will testify to this : "To anyone considering these heads, the Speedmaster heads I did my complete disassemble-home-inspection on were a true bolt on. Not only that, casting work was great! The EQ heads I just recently bought would have destroyed my engine. +1 for Speedmaster."