1970-1990 Chevrolet 454 Big Block with 168-tooth, externally balanced engines.As performance levels increase, an O. E. style flexplate just won't cut it and a stronger option is a necessity to prevent transmission and or converter failure. B&M has you covered with our high performance flexplate designed for 1965 1990 Chevrolet big block 454ci (externally balanced) V8 engines with two piece rear main seal. Features include high tensile strength steel construction to resist elongation and cracking, dual bolt pattern 10. 75 or 11.