Tszyu was a sharp-shooter with serious power and Pryor could be wide open and well off balance times. I can see a Tszyu putting Pryor on his ass once or twice but not keeping him there. Pryor could make it a war of attrition and I don't see Kostya keeping up. The Hawk stops him some time from round 9 on.
At 140? Well seeing as Pryor never fought anyone good or solid at 140, he eats shot after shot and loses: it Kosts him the fight...