Sounds like any METAL driveshafts would work much better than the stock sliders. The holes around the U-joints will inevitably wear out anyways, even if the rest of it holds up.
How "extended" is it? Would these still fit?
http://www3.towerhobbies.com/cgi-bin...&I=LXNTT8&P=ML MIP makes great stuff. They should hold up alright.