Todd Marsh is doing a lot with the bigblock versions of these heads. It is important to understand that the ProMaxx and the Sidewinder bigblock heads come out of the same molds in the same factory. They are given names by whoever is selling them.
http://www.mopartsracing.com/tmc/ Possibly the same for smallblock heads.

The "I have heard" monster is lurking in this thread. The newest version of ProComp also known as Speedmaster heads has received good reviews from Pittburghracer and the guy who used to call himself Dr. J, Bryce Mulvey. Possibly working with Bryce the PCheads have more meat in the short turn so the short turn radius can be worked on more without hitting water. I suspect that is what the heads pictured above are.

R.