Also IMO there is no magic/phenomenon about these heads. That would make them unique in performance than any other head. It is well documented the rockers are no better than the Indys. And the sparkplug placement is not a 'good' thing because, they are not angled.$$$ Oil accumulates in the valvetrain area and makes a huge mess when removing the valvecovers unless the heads get modified. Valves and guides are unique and that makes them expensive.$$$ Unless they have evolved since these issues I don't consider them a practicle choice considering the other heads available. But I'd guess you've already made your choice. I am just stating facts you may not yet realise.