Steering All Over the Place at 55mph+

UPDATE
I think y'all are on to it with caster. I found a shop in Dallas that works on classics to do an alignment and am am in the process of scheduling an appointment . But decided this afternoon to take a look for myself. The cam nut andjustment assembly is not even close to allowing for positive caster and eyeballing the ball joints it looks like I have negative caster. Before I jacked it up took an angle finder to it and have 2 Deg neg camber as well. I wonder I'm scared to drive it!

Attached are pics.

As far as the k member and 1967 idler arm discussion it looks like a post 67 idler arm which I assume means the k member was swapped along the way. I know it's irrelevant but thought since y'all have been participating in this thread you'd want to know.

After I have alignment results I'll let you know how off and more importantly how she handles when proper.

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