On my 11A66 built car I shopped around until I found correct "looking" Upper Ball Joints, then I used 5/16 in. Button Head bolts to fasten them in. Then I filled the Hex head with J-B Weld, then sanded it smooth and painted it. I'm not all that fussy about it being 100% original, but at a quick glance it appears original. Here's a pic.;
You can also see in this pic,.this is an "early" 67 Sub-frame, it has provision for J nut for the back Bumper Bracket bolt.