sorry i am so late to this thread
I bought the axle right behind this one (for $125) for my F-700 Ford To convert it to air ride.
Drilling the frame was quite easy although it took a most of a day.
I simply took the frame rails and clamped them on to the opposing side frame rail and used them as a pattern. I then took the pilot bit out of a hole saw bit and drilled away. I did have to do some "adjustments" to get the pinion angle correct.