Can I use my Spanish version of ManHunter 1 and run it from my Dosbox or should I play the original English version?

David can give a more authoritative answer; but if the only major difference between the Spanish and English versions is the language of the text, using Spanish is certainly okay; and even if there's a substantial difference that makes the Spanish version faster, it's probably still okay.

Do it. Any release of the game by Sierra is fair game.