the drz sm has the inverted OC showa forks and I belive the swingarm is different. You cannot take the S dirt wheels and put the on the sm.
If you want the true dirt setup with 21/18" you can take a RMZ 250 or 450 wheels and use them but you still have to use the oversize front and rear rotors from the sm. There is a guy on ebay that sells the setup (warp 9) for about 700-800 US. No spedo.
Don't do the SM 17" rims with dirt tire, that's getho and your asking for death.