The string spacing across the bridge saddles on your LP, or on a modern Gibson, is probably between 52 and 52.5mm, so over the bridge pickup it'll be about 51mm (older - much older - Gibsons would probably be narrower).
If you go for 50mm spacing, the strings will be towards the "outside" of the polepieces, with 52mm they'll be towards the "inside", so really one is as good as the other - take your pick! Personally I prefer 52mm for the bridge and 50mm for the neck.