shared the exact same bore and stroke, but the 361 used the larger "Group 3" block. It produced a maximum 136 hp @ 3000 rpm and 273 lb•ft @ 1000 rpm. 426 The with a bore and stroke of GMC inline six appeared in 1940s 4x4 Cab Over Engine (COE) trucks made in Pontiac, MI. Power ratings for 1955 were 190 HP @ 3200 rpm; torque 350 lb ft @ 1000 rpm. It also appeared in large GMC trucks in the 1950s ending in 1955. 451 The 451 was released in 1939 alongside the 361 and 426. It was the largest in the GMC straight-6 line until the 477 debuted late in the 1940 model year. It shares the same stroke as the 426 and 477, with a bore. It produced a maximum 146 hp @ 2400 rpm and 350 lb•ft @ 1000 rpm. It was replaced by the 477 and ceased production at the beginning of 1942. 477 The 477 was released late in the 1940 model year, replacing the 451. It was the largest in the GMC straight-6 line until it was replaced by the 503 in 1950. It shares the same stroke as the 426 and 451, with a bore. It produced a maximum 154 hp @ 2600 rpm and 385 lb•ft @ 1000 rpm. 503 The ; GMC inline six was more numerous than the 426 inline six, starting in 1950 and ending with the 1959 model year. In the 1957-1959 model years this engine was listed as 225 HP@3200 rpm and 436 lb ft torque @ 1200 rpm. The GMC 630, 660, 720, and 750 Series of the 1950s offered the 503. See also List of GM engines GMC V6 engine GMC V8 engine General Motors Atlas engine#LL8 (Vortec 4200) Duramax I6 engine References Straight-6 Straight-six engines