1989 Ford F-150 pulls to the left
 

Alright i was looking at a 1989 Ford F-150 yesterday. Its got 135,000 miles on it as well as a flowmaster exhaust. 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? Also might there be somthing wrong with the tranny?