Tires.... probably but I see you left out a few things on your list.

Check upper and lower ball joints.

Also remember you have 5 u-joints up front, three on the driver shaft and one at each wheel.

Also check out your engine mounts and tranny mounts. If the tranny mount is bad it can cause any unbalance in the drive shaft to to shimmy the front end.

If you have the original steelies on there be sure to pull them off and check for rocks and debris on the inside grove. It is hard to check them without removing them. A small rock can weigh an ounce and that is all it takes to throw off your balance.

Just thought I'd chime in once a year and you are the lucky duck lol