My Pontiac history book list a 287.2 ci engine for 1955. It was the first V-8 for Pontiac's. The 7.4 compression ratio engine with 1 x 2 had 173 HP. The 8.0 compression with 1 x 2 had 180 HP, the 1 x 4 carb engine had 200 HP. Its a 3.75" bore and 3.25" stroke. In 1956 they went to a 316 CI engine. The book does not mention GMC. Joe
