Have a regular Ed chamber, like the 6006x heads, but not the same as their MR 6007x heads. The ports are the same, with no machining at the flange. The seats are smaller, with a radiused counterbore, and will accept 2.04/1.57 valves nicely. I use them often for 390 Stock Eliminator engines. They really work well with 2.09/1.66 valves, because the ID of the seat is small enough that I can get all seven angles of my favorite valvejob in there without falling off a cliff. Recently, I developed a version of that head with a cnc'd chamber and ports, that works really good with 2.09 valves, as a budget alternative to the Street Pro Ports. I plan to test them on a 390 right after the first of the year. They are in the 165 cc neighborhood for intake runner volume, and I think they will be good for small engines or big torquer/pulling stuff without breaking the bank. Those heads out of the box, with the right valves and valve job, will surprise you.