The Rover's Buick-sourced V-8 has been stripped of its dual SU carburetors and inlet-air heat stove. Though they shared a common block, the Oldsmobile used Wedge-type combustion chambers versus Buick's semihemispherical shape. The big external clue is the Buick's four-valve cover bolts (as shown). The Olds head has five. Also, the Olds version uses six head bolts to the Buick's five. The blocks were machined to accept either head.