hot rods, kit cars, sand rails and late model engine swaps. All Cadillac Northstar V8s Oldsmobile Aurora L47 V8 GM 3.5L LX5 "Short Star" V6 Atlas pattern Atlas family engines use a unique bellhousing pattern which no other GM motors share. GM Atlas engine Pre 1964 Buick and Rover V-8 Round pattern 1961 through 1963 Buick/Oldsmobile/Pontiac 215 Aluminum V-8 1967 through 2004 Rover V-8 based on the GM 215 Buick, Oldsmobile, Pontiac (BOP) V8 pattern Post-1965 Buick/Oldsmobile/Pontiac RWD V8s Buick Big Blocks and post-1963 Small Block V8s Buick pre-3800 90° RWD V6s Jeep "Dauntless" 225 in³ oddfire V6 (1967-1974) and Buick 350 V8 (1969-1970) Cadillac cast iron V8s after 1967 (1968-85 472 and 500, 368 and 425) Starters are on the left (driver's) side on Olds 350-455 and Pontiac and the right (passenger) side on Cadillac 425/472/500 and Buick 225/231/3800/300/340/350/400/430/455. Four bolt holes and two locator pins are common to the Chevrolet, and B-O-P patterns. Some transmissions, most notably the TH200-4R, take advantage of this by integrating both specifications into a "universal" bolt pattern casting. Cadillac V8 pattern, pre-1967 Early Cadillacs manufactured before 1965 used a "round top" bellhousing very similar to early Buicks; around 1965, the bellhousing pattern was revised until the BOP bolt pattern was adopted in 1968. GM 4-cylinder pattern GM Quad-4 family GM Ecotec 4-cylinder pattern An example of this pattern can be seen to the right. GM Ecotec family (Generation I and II) GM LLT and late High Feature family GM Ecotec Generation III pattern The completely re-engineered Generation III Ecotec includes a new uniquely shaped bellhousing pattern. GM High Feature V6 pattern GM High Feature family References Bellhousing