One of the product designs developed in response to this market demand was the GM "Buffalo" bus, nick-named for the hump-back style of the roofline. Many features such as the split-level design from the Scenicruiser and the revisions introduced in the PD-4106 model were included in the Buffalo bus. Unlike the Scenicruiser, the Buffalo buses were available for sale to all operators. In fact, Greyhound eventually purchased a few of them; the last GM bus purchased by Greyhound was a 1967 PD-4107. Models First generation: GM PD-4107 and PD-4903 In 1966, GM introduced the PD-4107. Also known informally as "decks", these buses were similar in some ways to the Scenicruiser design, but had a larger "second level" with the first level reduced, and the lavatory was located at the rear. The 4107 was in length, and nominally (without lavatory) would seat 41 passengers (38 or 39 with lavatory). In 1968, the PD-4903 was introduced, a long version of the 4107 which nominally would seat 49 passengers (46 or 47 with lavatory). The PD-4903 was the first GM bus to use a 24 volt electrical system and was equipped with a third luggage bay. In the "Buffalo" bus, the driver sat higher than in the Scenicruiser, but the passenger compartment was no higher than the Scenicruiser's upper deck, so the Buffalo was not actually a double decker. The difference in the height of the front and rear roof was approximately one foot, giving a sleeker, more aerodynamic shape. These product lines used an airplane-like stressed-skin construction in which an aluminum riveted skin supports the weight of the bus, while a rigid wooden floor platform kept the buses structural shape. The engine cradle was hung off the back framing of the roof. GM's Buffalo models were powered by supercharged eight cylinder Detroit Diesel Series 71 two-cycle diesel engines, known as the 8V71N. GM buses used a unique "V-drive" configuration with a transverse mounted engine. The transmission was set off at a 63° angle to connect to the rear axle. The left hand rotating engines were canted backwards for maintenance access; in fact the only major components not accessible from outside the bus were the right-hand exhaust manifold and the starter, which were accessible from underneath and via access panels under the rear passenger seat. The entire engine–transmission–radiator assembly was mounted on a cradle which could quickly be removed and replaced for maintenance,