When you list our rigs and use the stock PHB, the axle will be pulled to the passenger side. A drop will lower the PHB and recenter the axle but,as said, the drop must be vertical. I have mounted a few and some required the factory mount to be ground down a little, usually the original welds, for the drop to sit correct. Also I always do this without the PHB mounted.
An adjustable PBH is usually used to lengthen the PHB so the axle will be recentered at the new lifted ride height. Since it is now longer, some have stock gas tank skid contact. If properly adjusted, and maybe some skid adjustments, there should be little contact.
In your case, stock PHB and a drop, you could fix the rubbing with an adjustable PHB but you would need to adjust/build it shorter than stock.
Steve, at Sonoran Steel, and I discussed the clearance issues and my replacement skid maximizes this clearance. Since you are rubbing your tank itself, you need to pull the axle to the passenger side.
Take a long level, park on level ground, hold the level vertical at your rear tires. Now measure the distance (the gap between the level and the tire or fender). This gap should be close to the same. If anything, the axle slightly to the passenger side.