GTR,
The Keeley Turbo Head has slots(or porting) in the head on the intake and exhaust sides of the head. I think the idea is to direct the charge of fuel across the head to improve combustion. A better burn would result in more power. And gawd only knows there's no such thing as, "Too much power!!!"
The heads on the K&B 3.5ss and 7.5 Pro also have a similar feature. The porting on the Keeley Turbo Head is smooth while the K&Bs feature finger porting.
The older K&Bs did show performance gains using the Keeley Turbo Head. I'm not familiar with how it worked on other motors.
I know Gary Preusse sells them - (630) 279-2451 - Gary doesn't believe in the internet so there's no website or e-mail. But, he's very willing to discuss things on the phone.
Jerry Dunlap