There is a pretty good dub of the first "season" (75 episodes) and the special "championship road." It is one of the "lost" licenses from Geneon. A lot of people were hopping it would be one that Funimation would save but so far no word of that happening.
The show later got additional anime that followed deeper into the manga story (called "Hajime no Ippo: New Challenger"). This second season didn't get licensed in North America, however, so no dub for that half.
You might need to look for "fighting spirit" the North American / Geneon name.