The first M-badged 5 Series is the M535i, which began production in 1979. The M535i is powered by the 3.5 L M90 straight-six engine which produces 160 kW (215 bhp). The sole gearbox choice is a 5-speed manual and 1,650 M535i cars were produced. Features include front and rear spoilers, sports suspension, Recaro sport seats, the steering wheel from the BMW M1, a dogleg close-ratio transmission, a limited-slip differential and larger brakes.
Source: Wikipedia (original)