No, a dumbell pullover tends to work the lats, chest and serratus muscles (Arnold used to use this as a flushing exercise and also, what he believed, to increase the size of the thorax/rib cage-argued to be impossible after puberty, but when looking at Arnie, you have to wonder). The triceps should only stabilise and help the rate at which the arm lowers/raises etc, the arms shouldn't have a bending movement, just a near straight hold, elbows slightly bent yet fixed. A skull crusher completely focuses on the tricep, being a good mass builder from the tie in at the elbow right up to the shoulder.