The big block 915 was the same basic casting, just machined 2 different ways, the 350hp got the 1.60 exh, the 375hp got the 1.74.

The 915 small block head was also the same casting, just machined 3 different ways, 1.88 int, 2.02 int, 2.02 int with relocated push rod holes.

Don't worry about the dash #, block castings also had them. There was some thought the lower dash # had less core shift but I believe that has been disproved.