F-150 Pulls to the left

Alright i was looking at a 1989 Ford F-150 yesterday. It all seems nice and everything its got 135,000 miles on it as well as flowmasters. The problem came on the test drive it. It shifted a little hard into reverse but that might be because it was parked on a hill. The problem is it was pulling to the left. The truck had a plow on it this winter but i was told that was the only winter it had plowed. My question is, was it pulling because of the plow or, it has newer tires on it and does it just need an alingment?

I think if the plow was to move snow off to the right, it might have an aerodynamic affect at speed to the left. I'd remove the plow have an alignment done, bet that'l do it.