Chip Hi T&D and Jesel's need head work to fit the assembly on the head. They are a full roller rockers. Bearings on the body and tip. They are rebuildable. Jesel needs a pre oiler to prevent dry start ups with large cams over 700" lift. I think all cobra motors should have a preoiler for pre starting anyway. Most roller rockers have a roller tip only. The body is either bushinged or the body rides on the shaft. I have a set of old Dove's that a put a .020 groove in the body to give oiling all around the body to slow the wearing out. They now have bushing in them that can be replaced. I am going with Ersons next. The Shelbys are nice but paying and extra 300$ for the name is silly. I have a 600" cam in my motor. I think that the supports for the shafts and stopping flexing is the most important for hard racing. Make sure you Check the pushrod lenght for the right size. You want to keep the rocker on the center on the valve. Smith Brothers makes custom pushrods at a great price and 24 hour turn around. Just remember you get what you pay for.
See what everyone else is running, I think Erson wins for mostly street driven cars and T&D, Jesel, and even Shelby win on the track side. Good luck Rick Lake