I had a very similar designed shackle on my 97' CC. They were called Velvet Ride shackles. They did make the ride a bit smoother, took out the jittery bumps. The thing is they only lasted about 5-6 years before the rubber sagged out.
I second they look just like the Velvet Ride's....put 'em on my '04 in '05 (they're still on it). Helped a little. I don't think it made $400 worth of difference on a shortbed, but maybe longbed guys would see better results. Maybe I should put some on my '86.....that chassis neeeeeeeds 'em.
I put a set on my 2011 F350 crew cab long bed, it helped a marginal amount, but I then put some better shocks (all four). The shocks made as much improvement in the ride as the Sulastic shackles.
I would recommend both... Its still going to be a truck, so don't expect a car ride.