It should be the smaller of the two - 10.4" IIRC, it will have a 403 casting # bellhousing, 621 casting # is the 11" clutch. HTH
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1972 SS 454 Chevelle LS5/M21/12 bolt 3.73 posi
1969 Malibu COPO L72/M20/12 bolt 3.31 posi
1968 Malibu LQ9/4L80E/12 bolt 3.73 posi
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