Jake Paul vs. Mike Tyson II is going down ... but not in the boxing ring -- the two former foes are putting it all on the line with a $1 million bet on the Katie Taylor vs. Amanda Serrano fight!!
El Gallo issued the challenge to Iron Mike on Monday ... saying he's so confident in the Most Valuable Promotions pugilist's chances this week, he's willing to throw down the huge chunk of change on it.
Paul hit up Tyson on FaceTime to admit the streets were saying Taylor vs.