I believe the key date
for HINs was 1972 for all boats manufactured in the US or imported here. For boats built before 1984: "HIN Formats Before August 1, 1984 The boat manufacturer must display two identical hull identification numbers, no less than one-fourth of an inch high, on each boat hull. The primary HIN must be permanently affixed (so that it can be seen from outside the boat) to the starboard side of the transom within two inches of the top of the transom, gunwale, or hull/deck joint, whichever is lowest. On boats without transoms or on boats on which it would be impractical to the transom, the HIN must be affixed to the starboard outboard side of the hull, aft within one foot of the stern and within two inches of the top of hull side, gunwale, or hull/deck joint, whichever is lowest. The starboard outboard side of the hull aft is the preferred HIN location for many manufacturers." See link for more data.
