I've never had that problem switching trucks to radials, radials alone is like adding power steering, the only trouble with going radial is putting way wider tires on, the trucks weren't "designed for bias ply", they were designed for narrow tread.... and I can't imagine why anyone would tell you to add power steering before they can align it .... check over the steering for loose/worn joints, which can cause similar symptoms,
make sure the tires are properly inflated, and find another shop that can properly align it, supply the manual if necessary
Bill
