How hard is the job to do without removing the radius arm from the axle?
The stud nut is on the top side and you should have clear access once the spring is removed. It's threaded into, basically an extrusion of the stamped axle beam. As long as you can poke the end of a propane torch about where the stud pokes through you should be good. Pulling the differential might make things a little easier. You might get it through the knuckle opening.
Side note, If you're pulling the diff, there is also a stud that runs vertically almost up against the radius arm that clamps on the differential, you may break the thin edge of the slot where it goes through the differential. It'll be fine when you put it back in, it's pretty common, it may already be missing.