Converter question

Need answer to something I should know by now....on stock 727 BB verters when did they stop with the drain plug. I believe.it's 74 was the last , but verts after that were the lock up kind.. need to know as I'm needing one and before I drive 50 miles to get it... Thanks
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'77 was the last year for the drain plug. Eliminated because of the introduction of the lockup converter in '78.