I picked up a 4" leg vise. It is missing a spring, which I will make and the wedge for the retainer is missing I will also make this have done both many times. I want to square the jaws and hopefully without having to do like the last few and put the whole thing in the forge and square the arms. I haven't even looked at it very closely to see what is bent or crooked.

If any of you guys have a sure fire way to do the checkout and squaring I am open to new methods.

When I get it straightened up it will be available for some new smiths around here at cost.

Mine suffered a similar malady.  I losened the large nut at the botton of the vice, aligned the jaws then retightend the nut, works well and stays square although it gets hung up once in a while, binding on the bushings near the screw.  I don't know if I would claim it to be surefire but it worked for mine.

The answer depends on the reason that the jaws do not line up.  Is the pivot bolt or the pivot hole bent, worn, or otherwise off-center?  First make sure that the pivot point is working properly, replace bolt if warn, straighten pivot hole if worn or damaged.  Then look to see if the main parts are bent and straighten accordingly.  Then if the jaws still do not line up, repair that area according to the type of damage, bend, or wear.