powersteering feels "twitchy" at higher speeds

[SMS]

I recently bought a 71 R/T (clone, fake, tribute). the car is absolutely fantastic. My only problem is that the steering when the car gets up over 40 starts to get too responsive. A slight correction of the wheel will swerve the car. It doesn't feel right. The suspension parts are new, not sure about the pump.
Any suggestions of what might cause this? I was thinking of adding a power steering proportioning valve to turn down the pressure. I rather find out why it is responding so hyper.

Thanks

[Bullitt-]

People find these old cars to easy to steer but I've never read that they were to responsive, if anything the converse. Based on my experience with other vehicles I would think that given there are no warn parts that the solution would be in the alignment. There are some suggested specs for use with radials that differ from the original specs. I'll try to find an post the link.

[Bullitt-]

http://www.cuda-challenger.com/cc/index.php?topic=67713.msg695679#msg695679

[SMS]

Thanks for the info Bullitt

[Chryco Psycho]

if the front suspension is set to stock specs it will feel twitchy , you need to put in as much castor as possible in the wheel alingment this adds load to the steering & makes it less twitchy

[LAA66]

 Castor, plenty of castor.