If you only want to use one motor than you can use the axles form a TXT-1/Juggernaut, a TLT-1, HPI wheely King, or Tamiya High Lift.

You will also need to get a tranny as well, a lot of the custom builders us a Stampede tranny, with tmaxx or revo drivesafts.

You can find everything you need on ebay, thundertech sells axles by themselves as well as other sites like rc4wd.com.

Im not sure if buying it all separate will save you much money, but you wont have any extra parts that your not using.