What seats fit a 1999 Yukon Denali 3rd row

Honestly, the best resource is your local GMC dealership. Their parts department can examine parts catalog data to see when seat frames changed part numbers. My guess is - you have a limited application model year pool to choose from, as things are constantly changing and evolving -- and safety is a big factor with seats. So check with a dealer and see what years and models match what years and models.