FWIW I found some "socket" part of the ball & socket parts on ebay in 409 stainless for around $50. Looked them up because at a time I was considering BBK's (or knockoffs) and wanted to mate them to my current short H pipe.
Couldn't guarantee that they would work but they look like they should, I can get you the link later when I'm not at work (ebay is blocked here)
Also, FWIW the only 1 3/4" primary tube headers that I know of are Dynatech, Pacesetter, and MAC; plus Kooks or Stainless Works if you order them that way. I've heard the ebay ones that say they're 1 3/4" actually aren't, I know they have BBK knockoffs that say that but I've seen where people have bought those and they were 1 5/8" just like the BBK's.