This is the custom hitch that will accommodate both stock bumper and underbed spare tire carrier.
http://s1312.photobucket.com/user/Deve1958/media/DSC00598_zpse731a8ea.jpg.html3 Pics. The center tab is where you bolt the center bumper bolt to on the back side. Not hard to make if you have a good square tubing bender which I don't so had to get that part done at the local welding shop.
My current project needs it because when the truck is done, I am making a pickup bed trailer that matches the truck.