Borgeson pitman arm

I don't know about b-body or how that applies to a-body. I do know there were two changes in a-body steering linkage. The pitman shaft size changed along with how the arm(s) attach to the center link. One taped stud goes in the center link from bottom up. The other goes in from top down. You now have grease fittings to the road. 73 and later has cotter pins to the road, along with the larger sector shaft.
So there is one pitman arm design that is needed a for interchange that Chrysler never produced. The only solution is/was to change center link and idler arm to the later model design But... I have read that a aftermarket vendor now does now produce and offer the special pitman arm needed for this interchange. I can't say who/where.
My personal preference would be the correct 73 and later center link.
Please note; If yours was a 67 model a-body you would be seeking a idler arm for that later model center link ( Another part that Chrysler never produced ).
Having a 68 means you could purchase pitman and idler for the 73 and later center link from your local part stores or any vendor.