Outer Limits 4x4 Board

My 80 series has a 4" lift with adjustable upper control arms. Looking at the drivers side arm the other day I noticed the lock nut was loose and found that it wont tighten up. It looks like it been loose for a while and has let water and crud into the thread and has rusted out, so tightening the nut just mushrooms the end of the front half of the arm.

Whats the simplest way to fix it? Can the arm be repaired?

Any one had this problem before?

my 105's the same, tore the thread out :(
weld it up, all good

Thanks Busted.

I'll pull it off and get the welder out :-)

Still havent pulled this out to fix it, and of course no-one will sell one control arm....