I model the Northern Pacific in 1953 in HO. I have F-7s, GP 7s, RS 1 and 3s plus a few switchers. Not really caring if it would be prototypically correct for one of my locomotives to be equipped with a snow plow; but, would be interested to know if other lines where equipping their locos with snow plows in the early 1950s?
Pilot-mounted plows were used on steam locomotives through the end of steam and plows carried right through into the transition era to diesels where they were just as common. bremner is absolutely correct.
I was running out the door to take the kids to school, the correct answer is to look at prototype pictures of your era, for the NP., I would assume that they would have had plows from the beginning , as for the SP, a Baldwin or an SD7 in Oregon would likely have a plow while an F3 in Texas wouldn't.