Use the search function, and do a search on SRV or Stevie Ray Vaughan. There have been several threads in the past about his tone.

All I can tell you is, he used a lot of gear to get his tone. But, typically, you can get fairly close with a good tube amp, overdrive pedal (such as a tubescreamer), and a strat. A lot has to do with how you play the instrument though.