Tall balljoints will fix the bumpsteer.
Factory spindles have some bumpsteer because the steer arm is too low. B-body "tall spindles" place it even lower... tall balljoints move it upward about 1/2" which is nearly perfect for eliminating bumpsteer.
As for the above reply, here's the "why" on tall spindles or balljoints...
http://chevelleforum.org/showthread.php?t=5