I've seen the thrust washer assembly same thickness and interchangeable with thrust bearings. Seems the thrust washer has higher load capacity and the bearings a little easier turning.
I opt for the thrust bearings when I replace kingpins and have a choice of kits/bearing type. To find those choices look in the catalog by size, not exact application, then cross your preferred kit back to application just to double check it fits the make and approximate model you're dealing with.

I agree, if the other side is good then fresh grease and leave it alone.

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-