Help! Front axle problem

[MJN]

Ok, I've got a problem with my '72 Blazer. The passenger side wheel has a clunk to it when you push on it by hand and at about 35mph and 60mph the whole front of the truck tracks from side to side and feels like the wheel is going to fall off. I replaced the front wheel bearings on both sides, the spindle on the passenger side, swapped front and rear wheels on the passenger side, tie rod ends, ball joints all look fine and feel good. It feels like a loose wheel but everything is tight. Anyone have any ideas what could be going on? I need my truck back since it's my daily driver and it's been broken since Monday and everyday after classes I've worked on it tryin to figure this out. Thanks for any help.