It's doubtful that your pin weight is actually 1,410 lbs. with a 10,000 GVWR fifth wheel... more like 2,000 - 2,300 lbs. loaded. (Have you weighed the truck and trailer hitched and unhitched with a full load?) This is still not particularly heavy, though. You are likely experiencing the results of towing a fifth wheel with a short bed truck on our wonderful roads and highways. With a 2008 2500HD you probably don't want the added weight of an auto-slide air hitch (which are extremely expensive, anyway), so a dampened pin box is probably your best bet. When we installed a Demco Glide Ride pin box on our fifth wheel, it made a world of difference in the chucking. MOR/ryde and several other companies also make very good dampened pin boxes. The pin box was one of the best investments we made.
Rob