Intruiging. Mr. No Chin vs. Mr. No Skill. I'd go with the bigger guy with weaker chin. Khan by decision. But dropped 2 times in the course of the fight.
I've read a story by Doug Fisher how he met Josesito Lopez the first time. Apparently he was the only guy that was able to survive the sparring with Valero around his wait class in the area. IMAO Khan biggest problem is not his chin but his defense. He will get tagged by Valero and he won't be able to take his power IMAO
Kind of hard to judge since we never got to see Valero fight at 140. However, I suspect he would have beaten the **** outta Khan.