GSP is a 170 pounder? didnt know that. all i know is he is a former lightweight and the reigning WW at UFC.
If there was any fighter who could do well in MMA, its Pac. Strong legs, explosive, fast, darting in and out style would be great for keeping his distance, jumping out the way and sprawling from shoots. If he learns a great sprawl, put him in there with primarily a striker, I think he scores a vicious KO.
Pac vs Noons interests me if Noons beats Diaz and becomes a world champion. The boxing rematch is also intriguing. The thing is, putting someone in MMA gives them loads of options but putting them in one combat sport and you are asking them to be specialists in that field or its even more likely a fighter will get destroyed.
Any boxer with great footwork and defense will easily beat any top UFC/MMA fighter. I attended UFC 118 and most of these fighters are your avg. joe throwing punches. There are a few good decent fighters, but even their top guys are very beatable. On that night esp. on the undercards the fighters which had boxing exp. easily won their fights with jabs. The Toney fight is all garbage, Dana White has excellent marketing skills, but Toney has been done with boxing for a while now and should be retired. They are trying to use him as an example, but Toney's style defense is not for MMA, but you take someone like Manny that moves around he would have an easy night with someone like Bj Penn. A boxer training ethnics and conditioning are just in another level.