Leaf spring shackle help

Megaparts USA
Spring Shackles A-Body, Leaf Spring Bushings/Hardware, 183-MRE151 Reproduction, NOS and Used Mopar Muscle Car Parts (megapartsusa.com)
Mancini
Mancini Racing A Body Set
O'Reilleys
Shackle - 1966 Dodge Dart | O'Reilly Auto Parts

Or if you're totally bucks down, grind the heads/welds down that hold the bolts into the shackle, insert new grade 8 bolts through the side plate & use the other side plate to hold them square. Weld the new bolt heads to the side plate.
Use new locknuts when reassembling.