Lower horsepower (designated Passenger versions by Chevrolet) big-blocks were NOT offered in 1965. The only big-block offered was the RPO L78 396 c.i. / 425hp (designated Hi-Performance). This is the engine that supplanted the fuel-injected RPO L84 327 c.i. small-block. Lower horsepower versions of the larger-bore RPO L36 427 c.i. / 390hp big-block would appear in 1966, as well as the hi-performance RPO L72 427 / 450hp (later re-designated 425hp) big-block.