I've owned my 68 KR conv. for 25 years. It is unrestored and presents very well, but the steering column always shakes at times especially when I hit a very small bump. I have had sets of new radials, balanced, aligned, replaced front springs, ball joints, rebuilt steering box. A local mustang restorer tightened the steering box adjustment, but the problem persists. Have any of you guys experienced this type of problem? Any thoughts?