That is the same "M" on my engines. My block casting numbers are also in front of the fuel pump. The casting numbers and date codes on Canadian engines follow the same format as the USA engines. The 261 engine was standard in small Canadian GMC trucks. The stamped serial numbers on the block behind the distributor did not use the USA format. On all three of my Canadian GMC 261's the stamped serial numbers started with a W. They did not offer 228, 270 and 302 USA GMC engines. 1954 and newer small Canadian Chevy trucks used the 235 but the 261 was available in bigger Chevy trucks. Truck engines had solid lifters, Pontiac car 261's have hydraulic lifters. As with USA trucks V/8 engines were available starting in the second series 1955 Chevy trucks
