Technically you "could" but there really isn't a class for 4x4 off-road 1/10th. The stampede is more of a basher rig.
Technically, racing anything is possible. You would be put in the 4WD class. However, like other people have told you, it's not designed at all to be raced. That shouldn't stop you from having fun, though. If you want to race it, then bring it out and race it.
by some short course wheels and a slash body and it is basically a slash 4wd, right? run it in the 4wd SC class. otherwise.. probably sportman class as is.. if we were talking racing local. but yeah. as sin said the pede is more of a bash rig as it comes, traxxas stuff can take on many forms though as so many parts interchange. here are some examples http://www.youtube.com/watch?v=ck8xrObgP6Y&list=PL1B4BF828BB2F9C63&index=3&feature=plpp_video andhttp://www.youtube.com/watch?v=Ob717J0NDB8&list=PL1B4BF828BB2F9C63&index=40&feature=plpp_video andhttp://www.youtube.com/watch?v=X3ZmrW-RIxU&list=PL1B4BF828BB2F9C63&index=41&feature=plpp_video check out ultimate rc for more..
Not thinking during my first post, I forgot I myself have a pede 4x4 that has been truggized and as I still wouldn't call it competetive I would say it's an excellent basher though! Look in the offroad section under new pics.