a 366 396 402 427 cranks are the same stroke the 366 and 427 tall deck cranks will work in any big block if you want a 3.76 crank .the new one pice tall deck 427 crank will not fit in a old block. mark4 . but a old crank two pice rear seal will fit in a new block with a seal adpater new block mark5-6 .the crank will need to be balanced if out of the tall deck