Axle Swap to upgrade to a 4.5" BP

George Jets said
Need to weld shut those 2 smaller holes on the axle flanges, machine them down flat, and then redrill for the 4.5 studs.

Leave the large hole open so you can get your socket in there so you can tighten the bearing retainer at the backing plate.

Then you'd only have placement for FOUR new studs on the bigger bolt circle..as the 5th would be in that big hole. You'd have to weld them all in and then use an old small bolt circle hole (enlarged) as your socket hole.