Others might respond regarding "modern" (sealed) tie-rod ends. Make sure you understand all that has to be replaced and matched-up, if you go "modern".
I use original-style ends/parts and have never had any problems - and, they are adjustable and greaseable.
If the GMC parts are similar to the Chevrolet truck parts (on 1/2 tons, I'd bet they are the same), repair kits and parts readily available (check the "Parts" section in "Links" (upper menu on this page). Full/expensive original-style tie-rod-end assemblies are also available for your size/rear Chevrolet truck.
