The Stovebolt Site Forums The Shop Area Engine Shop 1955 2nd Series GMC V8 identification

Assuming it is an original "GMC" V8 it is basically a Pontiac V8 from 1955 with dished pistons lowering the compression ratio from the Pontiacs 8.0:1 to 7.6 if I remember right. Look for the engine serial number on the passenger's side as shown below. The first 3 digits are the engine size. In 1955, Pontiac called the engine a 287 while GMC called it a 288. There are rumors in the GMC Master Parts Book that some of the 55.2 trucks came equipped with 316 cubic inch (1956 Pontiac 317) engines, but I've never seen one.

In any case, none of the Pontiac-based GMC V8 engines came from the factory with a 4 barrel carb. They were all Bendix-Stromberg WW-203 two barrel carbs.

Check the data plate on the driver's side door jam. A 55.2 model would have a serial number like 1028YP12345
where 10 is the model number, 10 is 1/2 ton, 15 is 3/4, 25 is 1 ton
where 1 is the wheelbase length, in 1/2 ton 1 = 114", 2 = 123"
8 is 8 cylinder. If a 6 cylinder there is no 6, just blank space
Y is the year. Y = 55.2, X = 56, T = 57, S = 58/59
P is the plant that the truck was built in, P = Pontiac Michigan, C = Oakland California
12345 these trailing digits are the actual chassis serial number.