improvements included a collapsible steering wheel and padded wheel hub, concave control knobs, elastic black rubber heater levers (instead of rigid coloured translucent plastic), and softer, rounded dash top padding. Door handles, locks, and window cranks were modernized and less protruding, the door pockets were elastic, the rear-view mirror frame was black plastic instead of chrome, and the side view mirrors became more angular. Essentially, the 1967 250 SL retained the more classic "chrome" interior of the 230 SL, whereas the 1968 250 SL introduced the modernized "safety" interior of the 280 SL. US models acquired side reflectors on the fenders, Kangol three-point seat belts, an illuminated automatic gearbox shift quadrant, and emission control equipment. The chrome horn ring was changed to matte finish. 280 SL (1967–1971) The 280 SL was introduced in December 1967 and continued in production through 23 February 1971, when the W 113 was replaced by the entirely new and substantially heavier R107 350 SL. Over the years, the W 113 evolved from a sports car into a comfortable grand tourer, and US models were by then usually equipped with the 4-speed automatic transmission and air conditioning. Manual transmission models came with the standard 4-speed or the optional ZF 5-speed, which was ordered only 882 times and thus is a highly sought-after original option today. In Europe, manual transmissions without air conditioning were still the predominant choice. Of the 23,885 280 SLs produced, more than half were sold in the US. The main change was an upgrade to the M130 engine with maximum power and maximum torque, which finally gave the W 113 adequate power. The performance improvement was achieved by increasing bore by , which stretched the limits of the M180 block, and required pairwise cylinder casts without cooling water passages. This mandated an oil-cooler, which was fitted vertically next to the radiator. Each engine was now bench-tested for two hours prior to being fitted, so their power specification was guaranteed at last. The M130 marked the final evolution of Mercedes-Benz' venerable SOHC M180 inline-six, before it was superseded by the entirely new DOHC M110 inline-six introduced with R107 1974 European 280 SL models. For some time, it was also used in the W 109 300 S-Class, where it retired the expensive 3 liter M189 alloy inline-six. A brief chronology of the most notable changes made to the 280SL: 12/1967: One piece wheel-covers (like W