Is what you're feeling a high spot or a flat spot? The bias plys develop a flat spot when parked, but it goes away after driving a few miles. That's part of driving these old trucks.
Radials will give a smoother ride, but are harder to steer due to the higher rolling friction. I replaced my front tires with bias ply, my dealer stocks an import from Mexico that's about $20 a tire less than a low dollar radial.
