JKS MFG. JKS OGS930 Weld-On Flange Spacer for WJ Knuckle

if your using a wj hub do you need this......or is it only needed using yj tj xj hubs?

How thick is the plate?

Why does it have to be welded on? Can't it just be used as a spacer when you bolt the unit bearing back in?

is the spacer needed for 2wd? i have no axle shafts, the entry hole is plug welded sealed.