GMC Truck produced a unique 60° V6 engine from 1960 through 1978. The engine was available in 305, 351, 401 and 478- cubic-inch (5.0, 5.8, 6.6, and 7.8 L) versions. In late production there was also a 432-cubic-inch (7.1 L) version with enlarged crankshaft journals. GMC also made a 637- cubic-inch (10.4 L) 60° V8 with twin balance shafts using the same general layout as the 305. Finally, there was a 702-cubic-inch (11.5 L) "Twin Six" V12, which was basically two 351s placed end-to-end with a common block and crank. A Diesel version was called the ToroFlow.