Car shakes

my front driver side tire will sometimes shake rapidly when im cruising at 40 mph on my 1969 vw bug. i dont know if it is my tie rod, or torsion arm. anyway to fix it? its not lowered or raised. it has disk breaks in the front. the bushings are worn because if switching from drums to disk. any ideas? any one selling torsion arms or tie rods for cheap? please help. one more thing. its not the alignment because when i let go of the wheel it doesnt drift off any direction.

Could be a number of things starting with loose wheel lugs,worn bearings,bad ball joints,worn tie rod end,worn beam axle bearings,to a bad tire.Start at the tire and work your way in.Something is worn,and its dangerous.

Most often the shake is caused by a bad steering dampner. That's the skinny shock absorber looking thing between the steering arm and the beam.