the unicorn knuckles are from '99-00 2500 Non- HD models. You can buy them new at 150 bucks a pop still, link here
https://www.rockauto.com/en/catalog/gmc,2000,sierra+2500,5.3l+v8,1359154,steering,knuckle,7496
Expensive, but so are the reamers and the risk of messing a knuckle up. I was lucky...