Hy Alex Arrow, Please remember to tell us what year, make and size of truck (model designation) you are asking questions about. If Frank50 has it correct that you are asking about a Canadian 53 GMC 9700, that truck left the factory with a GMC full precision bearinged six cylinder engine, probably a 248 a 270 was an option. 248 engine serial numbers in Canada begin with the letter G sometimes a second letter before the numbers begin. The engine you showed us the serial number of is probably a Chevrolet, if you realize it is shorter than the engine that belongs there then it is most likely a Chevrolet engine. If you could post a larger picture of the engine showing the valve cover and the cylinder head we may be able to confirm the make of the engine, hope that helps.
