I really dislike to get into a disagreement Panic, but I guess you have not looked in a parts book or compared shafts.
GM group 0.353
If you look through different year parts books, some will note a different shaft with a flat spot ground the full length for hydraulic lifter engines, but later books combined them all to one part number.
Here is a
LINK to the 1957 parts book. Group 0.353
