Help with front end vibration/wheel bearings

[jrpitdog]

So I have a rebuilt/slightly modified 2wd 66. I bought it already built. The front end has mid 80s 3/4ton spindles and hubs with disc brakes. The truck was built only a few years ago, the entire truck either had new parts or rebuilt parts installed. Truck only has about 10k miles on it since the finished rebuild. I drive this truck a few times a week to work on the freeway, it has a 700r so I scoot right on down the freeway. Last week I noticed some vibration up front at higher speeds, actually it was most noticeable around 50-60mph then got a little less noticeable above 60. When I got home I jacked up the front end and grabbed the wheel at 12 and 6 and got a little play. I took off the dust cap, pulled the cotter pin and checked the castle nut, I could back it off by hand, so I tightened it down just until there was no more play, both wheels were like this. Next day I drove it and the vibration was noticeably less in the morning, but on the way home it was the worst it has ever been, I almost pulled over and got it towed because I thought the wheels where going to come off. I got home and before I pulled the hubs I checked the bearing play and couldnt detect any???? I pulled the hubs and visually inspected the bearings and races, I cant see anything wrong with them at all. Granted I dont consider myself a bearing expert but I cant visually see anything wrong with them, and they are quality USA bearings (NDH). I do notice uneven wear on the outside edge of both my front tires. All the tie rod ends, ball joints and bushings are new, everything seems to be tight. It dosent pull on the highway either. So now Im just looking for some advise. Anybody have a good way to visually inspect for wear on bearings? I remember hearing something about holding the bearing vertical and squeezing against the cage at the bottom or something. I know I should just go ahead and replace the bearings, get the tires rotated and balanced and have the front end checked and aligned and see what comes of that. Im just baffled by this vibration with no apparent cause.