Early Mercury's are great cars for lines.
But none had the grill like that one. Here is a 53 Monterey.
http://i1166.photobucket.com/albums/q602/yoseft1/1953-Mercury-Monterey-red-black-friend-sy_zps35033896.jpg
You're good, I think the one looks like maybe a 57 Buick Century? The 59 Chevy Biscayne guess looks good too. I have a lot of farms on my route that have old pick-ups sitting out in the field that look like they didn't start one day, so the farmer went to town and bought a new one. They didn't seem to trade them in, they just kept them and parked them out in the field.