@JohnMartin Sorry, I stepped away and did not see your posts. Bullinger says, "Methuselah = When he is dead it shall be sent, i.e. the deluge" (The Companion Bible, note on Genesis 5:21).
Tradition appears to support this. I am not sure how the year he died could determine if he died 7 days before the flood or in the flood unless it was on the break of the year.