You'll definitely want to look at your original pickups when it comes to 50mm vs. 53mm. I have 2 Gibson SG Standard Limiteds (2011 and 2012 models), they both came with F-spaced (53mm) pickups (490R/498T), and it's my understanding that this is more and more common on the recent Gibsons. In my case, the long-leg 53mm Warpigs and Mules that I bought fit perfectly and look great. I had a set of 50mm pickups in one of them and it just looked wrong.
Of course, there's always the argument that long-leg 50mm will have better resale value, so keep that in mind. Plus, it's debatable that it'll make a huge difference in sound in either case, for the same reason that bent strings don't drop off in volume, unless the string is completely off the pole piece.
miserymoth, to clarify: for my guitars, I bought long-leg 53mm calibrated sets. Both pickups are long-leg, but only the bridge pickup will be 53mm (the neck is always 50mm). They fit perfectly. If your SG Special Faded has an F-spaced bridge pickup, they should fit perfectly in your guitar as well.