Ok, here is a link to my truck... this mod has the Swamper rims on it, I drilled a hole thru the middle to reach the lock nut. On the back side of the rim I super glued a stock Xmod truck rim to it. (just look good at the photos) I like this way better because the xmod rim makes it a lot more stable and less woble then the axle stub extension mod. Just use some strong super/ca glue and let it cure for a day or two before messing with it.. also sand the contact surfaces good before glueing.
http://www.xmodsource.com/forum/showthread.php?t=15034
Here is the axle stub extension mod.. also good, you decide which way you want to go.
http://www.xmodsource.com/forum/showthread.php?t=12765