Both guys were rarely in boring fights, would be a fun one. Norris 7 out of 10 i think. Although Vargas was nicknamed 'Ferocious' i think he might have been a bit too patient for a guy who hit as hard and as fast as Terry. On the other hand (let's say the 3 out of 10) it might suit him well against a guy with a poor chin and lapses in concentration. I can easily see Norris ahead on the cards, get a bit too comfortable and get smashed by clean shot.
Norris would control the fight for the most part, and stop Nando late. Although he'd probably have to survive a few scary moments along the way. But in the end Norris has too much handspeed, and Vargas would have no way of avoiding Terry's left hook.
If that happened, there would definitely be an instant rematch and Norris would bring his A game and win. Like X said, Vargas would have problems avoiding that left hook, though. Nando had trouble with Tito's hand speed and Terry was even faster, and was a very good defender when he was on. Norris TKO 10
Vargas has skill and he has a puncher's chance (it's Norris, whose chin was as durable as fine china) ... but I tend to agree that Terry's speed is too much and that combined with the left hook (which Vargas always had trouble avoiding) is too much to overcome most times out of 10
I can see Norris outboxing Vargas to win by decision. But I can also see Vargas' punk attitude getting under Norris' skin enough to make him lose his cool...and give Vargas a better chance.