I used the standard Tamiya truck springs on a tlt axle, it raises the chassis height by about 10mm, to level the chassis I redrilled the rear suspension mounting holes 10 mm lower and left out the big Tamiya cross member and made up a piece of steel and fitted it to the bottom hole to steady the suspension brackets on this model,
http://rctruckandconstruction.com/showthread.php?t=6044