I don't know of anyone who uses these, but on paper they look great. The best of all worlds. Small ports for good velocity, low end torque, yet higher overall flow than any two valve head, plus the perfect center plug configured combustion chamber. AND, . . . . . Everything bolts up to all the stock "stuff".
I would love to know of someone who actully uses them to know if they are as good as they sound. My Northstar Caddys are little 4.6 liter engines, and with their four valve heads, they haul ass. Same should apply with these heads.
Here:
http://www.araoengineering.com/Ford/frdsmb.htm
Ed