New 56742 Cylinder Block 2.9 / 3ltr VB6 series with engine no's VB6J/K, 

Note: on an Aston Martin or Lagonda built from 1949 to 1959 the engine number is on the timing cover as the cylinder block was considered to be a consumable, as such a new block isn't a disadvantage to the cars provenance, in fact it enhances it.