I'd take Chang. I've never seen Johnson deal with someone faster, and I think if Chang takes his boxing seriously and puts the skills he showed against Torres to use, he'd win a clear decision. Johnson was very good, but Chang is one of the greatest little guys I've ever watched.
I favored Too Sharp before mainly because he was the “bigger” fighter and Chang didn’t seem to find success at Flyweight although he was already passed his prime at that time. Rethinking this fantasy match I think I might favor Chang stylistically speaking. If we were to go by peak Chang being able to make 108 easily then I can see him outpointing Johnson in a close fight. Chang was an absolute beast and a very cunning, quick, formidable fighter that Too Sharp hasn’t faced before. It’ll be a barnburner of a fight with both guys going at it throwing lots of punches but I think Chang’s quicker feet and unorthodox attack will befuddle Johnson.