When i rebuild Gen 3 MII sway bar links i use Spohn performance Spherical end links with poly bushes. Their part number is..
Application: 1967-1973 Ford Mustang
Spohn Performance
Part# SEL-19-408
https://www.spohn.net/shop/1973-1977...GM-B-Body.html
NOTE: Centering spacers will need to be machined, i use stainless tubing 1" OD X 3/8" ID. You will also need to make or reuse your old clasp (lower mount) on you control arm.