Yes, the stock half-shafts may have had the original u-joints replaced with Spicer u-joints. From the article I read it appears one obvious indication between the Spicer and the original half-shaft is the amount of metal added to the stock unit for balancing. When I compared the stock unit to the Spicer I noticed the machine work on the Spicer to be much nicer as were the castings.
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