The problem is that there is probably a separate brochure for Canadian Police '54 fords. There is one for the USA built '54 Fords and there is a slightly different engine line-up showing the Mercury 256 Y-Block as the Police Interceptor engine. So still not positive if it was possible to get this engine in Canadian police cars. I'm thiking they came with 255 Merc flatheads since it still had the old (1953) Ford frame w/o ball joints.
Just my opinion.
As I mentioned before, there is a 1954 Ford (USA) Police car brochure on the "Old Car Manual Project" on-line to look at.