Steering Problem -Need assistance

So, I'm leaving my driveway today in my 72 Duster and I cannot turn all the way left. The wheel only travels to the left about 1 turn, then it stops, and of course it will max out to the right. I was looking at the pitman arm and it seems to be hitting my header on the drivers side; not allowing the wheel to turn over 1 revolution. I just drove 1200k last month with no problems, so I am stumped. Can the problem lie within the power steering gear? Please advise