all bbc parts from mark 4s can be swap around .like rods .cam. timing sets .tin . head bolts if stock heads. cranks are 4.000 two pc rear seal fit all the same iron or steel. 4 bolt mains have nothing to do with parts fitting as a stock two bolt block is the same block less 4 bolt caps and machine work .i have put 4 bolt caps on 454 and 396 blocks