From 1946 to 1968, Ford offered the Mercury M-Series pickup trucks that literally the F-Series lineup of the day. Only offered in Canada, the M-Series trucks are rare collector's items now, but depending on which car shows you attend in Canada, you may still see the big Mercs still on the road.
If you want to know more about the M-Series' history and the various models offered, we found this informative piece at Autonet.ca by Glen Woodcock. We also found this front-view spotter's guide to help with identification issues. You'll note the guide goes to 1972 because it took a few years to sell off the remaining inventory once the Oakville Assembly Plant shut down.