My 2000 Astro Van sways going down the road.

Tires are a start. What suspension parts beside the steering box was changed? Sway bar tight or broken? Wheel bearings good? Put it up on a jack so the tires hang down. See if there is any play in the wheels from side to side. Any noise when you turn them? Tie rod ends good? Springs good? with the van on the ground, step up on the bumper and jump off. Does it spring up and stop or continue to move up and down? Shocks? I'd place my first look at the tires. I had similar issues with my car and a vibration at freeway speeds. New tires stopped all that.