Help: Stripped Shock stud on Rear of 88 Cherokee

Hi:

I've got a stripped shock mount stud thread on the rear axle (D440) of
an 88 cherokee. I've been looking at various options to clean it up
including:

Cutting off the stud and drilling a hole for a new stud or bolt

Rethreading what's left of the threaded stud to the next size smaller
thread.

I like the second option as it doesn't involve welding. My question is:
if I want to re-thread to the next smaller size, how do I know what the
next smaller standard size die is that will fit over the now stripped
stud? I measured the size of the formerly threaded part of the stripped
stud and I think it's just under 1/2 inch.

Thanks for any adivce.