I bought this car because it has no rust. Perfect project car. No rocker panel rust, no trunk lid rust, etc. It runs and drives fine, burns a little oil, tranny/clutch great. Wheels are in good shape. COLD AC. So far the only problems I am aware of are the support bearing for driveshaft seems shot and I need to balance the wheels/tires.
If the car shakes at higher speeds and that bearing shot, then I would venture to say that is the reason the car is shaking, not the wheels/tires being out of balance. Nissan 2 piece driveshafts are a PITA, but I bet if you replace it, the vibration will go away.