The axle could be bent, but it is really hard to tell for sure without measuring for sure. When I am in doubt a beam, I use one of these
http://www.wheel-a-matic.com/page11.html I lay the beam on its side and stick the gauge to the bearing area of the king pin bore. I adjust the axle to where one side reads 0. I then measure the angle on the other side. A degree or 2 won't hurt anything. If I find a twisted beam on a salvage truck I bought, I throw it away because they are plentiful. However, on a 50 year old vehicle it might be worth your while to straighten it. It doesn't take much to bend an axle, but it takes a steady hydraulic push.
