I took my '84 Thunderbird to get an alignment and all four wheels balanced last Monday afternoon but I'm still getting vibrations through the steering wheel at around 50mph. This is what I've done so far to try and remedy this issue:

1. Installed a new vibration dampener (harmonic balancer).
2. Had new U-joints installed on driveshaft and had it balanced.
3. Installed new front struts.
4. Had car aligned and all four wheels rebalanced.

I've also jacked up the front the car to check for play in my tie rod ends and wheel bearings but there doesn't seem to be any issues with either of those items. The work I've done so far has greatly reduced the severity of the vibrations but they are still present and I feel I should be able to get this car to run smoothly at highway speeds. Are there any other items that could contribute to this issue that I need to check?

Thanks!
Dan