Lower control arm issues, Damaged thread, 1965 C10
 

Hello all,
after many years of fun with my 1965 C10, it's time for an overhaul of my front suspension.
Unfortunately I'm struggling with the reassembly of the lower control arm. It seams that one of the inside threads of the control arm is damaged. It's not possible to mount the bushing of the control arm shaft.
Does anybody know the dimensions and pitch of this special thread?
Is it's possible to rework it with a screw tap or a thread file?
Thanks in advance.
Martin