If you wanted to use slayer wheels and tires, a set of savage or lsp axles should do the trick. Then you can use the hpi 14mm netal hexes, and I am sure that the slayer will use 14mm hexes...unless traxxas goes with the new 17mm stepped hex they put on the revo platinum. I figure that they will stick with 14mm hexes.
The savage axles fit if you are using dogbones on the buggy. You may be able to swap out the cv style axle ends if you are using cv axles on the buggy.
http://www3.towerhobbies.com/cgi-bin...&I=LXDLE5&P=OW
http://www3.towerhobbies.com/cgi-bin...&I=LXDVK2&P=OW
Ofna hyper buggies are nice, but the ofna gtp solid center spool will not fit the hyper bulks, bearing sizes are different... Not sure if there is a solid center option for the hyper buggies.