2 wins over Reggie Johnson and one over John David Jackson were probably his best. He was a good fighter but he had like 120 fights in Argentina.
Tough man Castro. Hes got one of the best come from behind KO's ever for me against Jackson. Finished, taking a beating, then out of nowhere he caught him absolutely sweet !
One of my favourite fighters growing up. Only stopped twice iirc. Once when he was about 105yo and the other was up at cruiserweight when he was fighting for the WBC title against Gomez and was stopped in 10. He also fought Jirov for the IBF and lost on points, up at 175 he beat Harmon, lost to Briggs and Jones jr. He beat Mayfield and Whitaker, throw into the fact that after he TWICE beat Johnson at 160 Johnson went up to beat Guthrie and become a champion at 175. He was as tough as teak.
He's as "famous" as he ought to be. Fans of his era, including casuals, know him, as do boxing nerds/historians studying the era, but that's about it and that's fine. He was good, not great.
Why isn't Jose Luis Ramirez or Yori Boy Campas more famous? They fought over a 100 fights in the modern era too. The answer is because they were good but not great. They weren't like Julio Cesar Chavez or Roberto Duran.