I want to pull a laser drag scraper using automatic blade control through my laser equipment with my D6D SA. It is my understanding that the D6D SA has an "open" center hydraulic system. I'm told that "newer" tractors use "closed" center hyraulics and are better suited for such automatic laser work. I understand the general concepts of "open" vs "closed" center hydraulics but how does it relate to automatic blade control? Is there a special hydraulic valve that can be included with the setup to make the tractor suitable? Anybody else using their older Cats for such use?

Delta, closed center hyd generally use a load signal to up stroke the pump to produce flow on demand. You would need a piston pump and valve bank that matched to make a closed center scaper control.
Later Bob