It's pretty easy to check the bump-steer.
1) Make a legible mark on each tire in the front where you can span a tape measure to check the distance.
2) Lower the front end using the torsion bar bolts as far as it will go.
3) Measure the distance between the marks.
4) Roll the car forward until you can measure it behind to the same marks.
This will give you your toe setting.
5) Now raise the car until the tires are almost off the ground with a floor jack under the K-frame.
6) Measure to the same marks again.
7) Pull it forward and measure again.
This sequence of measurements will tell you how much bump steer you have. You can alter the steering box angle and/or idler arm angle (by slotting the hole that the mounting bolt goes in) to try to minimise it. When you get it right where you have no or at least minimal toe change by changing the front end height weld a washer over the hole to maintain the location of the idler arm. You'll know that this is way off if the car steers itself when you go over dips in the road after it's aligned. Most all of them can use a little ajustment. I altered my old '68 Cuda by about 1/8" on the idler arm angle to make it almost perfect.
