Hot Rods 32 roadster shimmy

I have a deuce roadster and can't seem to solve a 70 mph shimmy. Bumps generally start it, but even on a smooth road there is some shaking at that speed. The wheels are balanced. The axle has a panhard rod but does not have steering damper. The axle is located by hairpins.

 

Wheels show any lateral runout?

Are you running radials or bias ply? Bias ply tires can be out of round and need to be trued in order to get a shake free ride. Maybe you have a broken belt in a radial?

I know it sounds silly, but are the lug nuts seating tightly in the taper on the wheel?

 

Check for King Pin slop,Just went thru the same thing.
Everything in the front suspension was tight.
ckecked the king pins and had a very slight tic in em.
Swapped out kingpins and problem solved/

 

You might also find something if you search "Death Wobble" been a lot of posts on it, and a good majority seems to be on the roadsters...I hope you get it figured out soon.