Why wouldn't you gusset the axle while it's out? I don't think the necking down on the ends is a problem, but having witnessed the effect of a semifloating rear with a bent housing (ie wheel and shaft leaving the truck at ~45 MPH), I would do what you could to strengthen the housing while it's out of the truck!
I would also do a FROR full-floater, but that's considerable $$$ that can wait for later.
