Won Hyo
When people notice similarities between Chang Hon patterns and older Karate patterns, the example they always point to is Won Hyo. Not only does it contain 80% of Pinan Shodan/Heian Nidan, the movements appear in the same sequences and at the same point in the pattern.
Won Hyo is Pinan Shodan.
The following videos were used as reference:
ITF Legacy performance of Won Hyo.
Hirokazu Kanazawa performing Pinan Shodan (Heian Nidan).
The openings of both patterns, repeated on both sides, are identical, save for Won Hyo using a knife hand.
They both proceed with a side kick, Won Hyo to the front, and Pinan Shodan to the rear. They both land facing North in a back stance with a knife hand block, followed by two more knife hands and a spear hand.
Won Hyo (pictured below from the side angle) then repeats the beginning, which Pinan Shodan does not. Returning South, however, both patterns are identical:
-turn South into a front stance, execute circular block / inner forearm block
-front kick
-punch
-repeat
The above block is often referred to as an "inside block" in modern Shotokan literature. Choi's 1965 describes the block in "HEI-AN PATTERN II" as a "circular block," meaning that Won Hyo is performed the same way that Choi performed Heian Shodan.
Won Hyo's ending kick and forearm guarding blocks do not appear in Pinan Shodan, although knife hands to both sides
appear when Won Hyo repeated the opening section.