A 2007 5.7 liter is rated to tow 9100k pounds so you can pull the trailer weight with your pickup. Towing a 5th wheel with a 1/2 ton is not recommended though as it does not have the same heavy duty axe, spring, frame, ect. as the 2500 or 3500. Saying that I have seen it done. I guess if you were to upgrade brakes, add more leaf springs and air bags, and get an adjustable sliding 5th wheel hitch you could do it. Your owners manual will tell you the maximum towing capacity. You also have to figure the 8k pounds is just the trailer if you add clothing, kitchen items, ect. in the trailer and pickup the weight will go up. I wouldn't suggest it but it can be done. Would be interested though to see pictures of it and hear how it handles for you if you do it.