Just able to get back. Last Friday I brought the car into our local military installation, where I am able to use the auto craft garage. They taught me how to use the computer wheel balancer, and I went through each tire. It turns out one of the front tires has a slightly bent wheel, and there was a lot of weight on there to compensate. The tire was out of balance anyway. We took off all the weight and started over, but in the end it still took a lot both inner and outer. Two other tires were balanced okay, and the fourth needed some work. I moved the bent rim to the rear. At the magic 65 to 75mph, the car drove a lot better - with no vibration. I checked everything else, including the ball joints and all is good. Thanks for the input everyone, I appreciate it.