Chrysler made three different casting of the 1957 and 1958 392 blocks, the A1 being the best and strongest, the WW, I think that was the casting letters on them was in the middle on strength and core thicknesses and the no name or letter blocks number block with weak main webbing with cast in holes between the main bearings and the bottom of the cylinder bores were the worst as far as strengths .
IHTHs