passenger seats also were optional on the base model. For 1970, a rear-wheel drive model was added, and the truck was also rebadged as the GMC Jimmy. Mechanical There were four choices for power plants, matching the contemporaneous pickup truck options: the 250 straight-6, the 292 straight-6, the 307 V8, and the 350 V8. There was also a choice between a three-speed automatic transmission, the Turbo-Hydramatic TH350, or one of two fully-synchronized manual transmissions: a three-speed, or a four-speed (SM465), which included a "granny gear" low-ratio 6.55:1 first gear. The 350 was offered only with the SM465 or TH350; manual locking front hubs were optional. The four-wheel drive version had a solid front axle and used leaf springs front and rear. The two-wheel drive version came with independent front suspension and rear trailing arms, both with coil springs. Both versions used drum brakes on all four wheels until 1971, when the entire GM light truck line was fitted with front discs as standard equipment. A tachometer was optional. Two transfer cases were offered: the Dana 20, available only with the manual transmissions, or the NP-205, available with both types of transmissions. The Blazer had of ground clearance and an approach angle of 35°. Engines 250 in³ (4.1 L) I6 (1969–1984) 292 in³ (4.8 L) I6 (1970–1971) 307 in³ (5.0 L) V8 (1969–1973) 350 in³ (5.7 L) V8 (1969–1991) Transfer cases NP-205 - gear driven part-time four wheel drive Dana 20 - gear driven part-time four-wheel drive 1973–1991 Overview For 1973, GM's line of full-size trucks was redesigned and updated; internally, GM named this the "Rounded Line" generation, while the unofficial nickname was "square body". A tilt-steering wheel became optional. Although rear-wheel drive Blazers were manufactured until 1982, the majority sold were four-wheel drive. As tested by Popular Science in 1973, a K5 Blazer with the 350 V8, automatic transmission, and full-time four-wheel-drive accelerated from 0– in 22.5 seconds, with an observed fuel economy of at a steady . With the standard 250 I6, automatic transmission, a 1974 K5 Blazer returned fuel economy of at the same speed. The 1973–75 K5 Blazers were equipped with a removable convertible top. In 1976, a half-cab design was introduced and used until 1991. The second generation K5 models incorporated the rear hatch glass and tailgate into a single unit, which allowed the glass panel to retract inside of the tailgate by use of a