Ok...
Per a Gibson QA employee, Gibson humbucker factory default heights are (with the high and low E fretted at the 22nd fret):
Bridge: 2.38252 mm high E, 2.38252 mm low E
Neck: 2.38252 mm high E, 3.175 mm low E
My 2012 Gibson Les Paul Studio (Burstbucker Pro pickups) came from the factory after Plek with:
Bridge: 3.57124 mm high E, 3.57124 mm low E
Neck: 3.57124 mm high E, 3.96748 mm low E
My 1994 Gibson Les Paul Standard (498/490) came from the factory with:
Bridge: 3.175 mm high E, 3.175 mm low E
Neck: 3.175 mm high E, 4.7625 mm low E
...just as a starting place, then shift up or down half turns of the height screw until the sound is in the sweet spot for the pickup.
FWIW I tend to get each pickup sounding it's best on it's own and just use the volumes to mix in middle positions. (I know some people will bias for the neck or the bridge and take what they get in the middle, or adjust heights for volume balance more than tone.)