Just sold on EBay (not to me, sadly) is a kinda rough Topping display model of a little known proposed variant of the Atlas space launcher, the SLV-3X. This design had a widened body, from ten feet to 12 feet, 7 inches. This allowed for more propellant to be carried without lengthening the vehicle, meaning that the existing launch infrastructure could be used. Additionally, the MA-5 sustainer rocket engine would be replaced with a higher thrust H-1D engine. See HERE for stats.
The SDASM Flickr account has a nice illustration of the SLV-3X/Centaur. See their site for the higher rez image.