Miller, Seeing your pics I would have to agree with 2ManyTrucks. Your engine could very will have come from a Canadian truck. Their serial numbering was different from US made numbering sequences. We've had several examples of Canadian built engines with letters at the beginning of the serial number sequence. The Canadian engines though did often use the same casting codes for the block and heads. The first picture you added shows the block manufacturing date code CON4 K123. CON4 stands for the conveyor the engine was built on and if the other follows normally accepted GM date codes K = November, 12 = 12th Day of November and 3 = 1953. That late in the calendar year could very well indicate a 1954 model year engine.
If you look elsewhere on the block, there should be a 7 digit numeric casting number which would be the block Casting ID#. Usually located just above the oil pan mounting rail on the passenger side of the block forward of the distributor. Unfortunately it is one of the areas where lots of gunk and road dirt build up which could be hiding the info.
Perhaps you can dig a little deeper and provide another pic or two?
