The MXR Distortion III and the Classic Distortion are exactly the same pedal. So this mod will work with both. Here’s what your pcb will look like.
Stock these pedals are really not too bad, but with the mods applied this is one awesome OD. In fact, this has become one of my personal favorites. This is a great pedal after the mod to use to juice up an existing overdriven amp or to place in front of a clean amp. Very nice distortion. The 3-way switch makes this a very versatile pedal. Middle position allows it to be used as a boost.