I've replaced everything on my son's 67 mustang steering. All new upper and lower control arms, new springs, new perches, Global West adjustable strut rods, Locking eccentrics for the lower control arm. All new tie rods, drag links etc. I had it aligned to proper specs. It still has a problem, it seems like it doesn't like to center. When you are driving straight it wants to roll over center and dart one way or the other. It's not as bad as before but it is still dangerous and I don't want to turn my son loose in it until it is right. Any suggestions?

 

It might be your steering box. Mine has a spot just like that at the center, where it feels ok off center but in tge middle it is dead and when i pull to one side or the other it feels that i have pulled it over a bump in the gear.

 

I take it you've done the Shelby 1" drop and verified that they aligned it to the shelby specific settings by checking the alignment print out?

If you haven't done the drop you also have to remember that these cars also originally rolling on bias ply tires and newer tires may require some custom alignment (read old school mechanic and not just setting the lasers on a new machine) to get it to drive the way you want.
Jon