According to my book on Monarchs, they used Ford dashes in 1946-48. I don't know if that would be a problem or not but something you might want to check.
The dash between the Ford and Mercury isn't all that much different structurally but I'm not as certain with Ford of Canada. The Ford and Mercury cars used the same basic Zenith Adjust-O-Matic radio for 1946 & 47. The type changed slightly for 1948 but it is hard to tell them apart. Model 6MF080 and 6MF780 were used by Ford Dearborn.
Here is a picture of a Barn Find 1947 Monarch dash panel. The reason why the Monarch used the Ford Dash Board, is because they were sold in the Ford Dealers, and needed to be identified as a Ford product, not a Mercury product. I hope that this picture helps.