I have a 1990 740 wagon, 200K miles,

the driver side ball joint doesn't want to let go,
I did the other side a while back and a pickle fork n'ammer got it out after a few whacks.

This one doesn't want to cooperate with my 3 lb hammer.
I'll buy a ball joint seperator tonite and have another go Friday and saturday,
but on the off chance that the seperator doesn't work I know the whole assembly needs to come
off, I plan on installing new cone bushings and sway bar links anyway.
My question is this, one of the bolts holding one of the links , is it the radius rod?,
it has a strange looking socket, its a star shape, male end, so I need a star female socket ...
but what size? whatsit called?
I'll buy a set but want to be certain its IN the set.

Cheers, Gerard