Cannot find the info anywhere.

I am going to be getting a free Sigma 8mm f4.0 lens. I already have the f3.5 version. Will I be able to simply remove the ring clamp from the 3.5 and put it on the 4.0? Is the NPP point in the same place or will I need to go through the calibration exercises? My 3.5 needs repair and I want to use the 4.0 while I wait.