Well, I went with the muratic acid and it worked. Soaked an assortment of smaller parts & plates for almost 24 hrs. here's how some of the pieces came out.
It worked great for removing rust & gunk, and didn't touch the small areas that still had chrome remaining.
The bobbin assembly (not shown here) is completely cleaned up but needs some polishing to make it usable - maybe . . . more pics to come.