That is a lot to ask, in one sentence, and can't really be done without making some assumptions... However I would say yes it would do pretty good of a job cooling it... IF, and only IF, you do a good job cooling the pelt. The only way to really know for sure is to try it... The outcome depends on how well you execute the application.
Keep in mind that the heatsink needs to completely contact the entire hotside of the pelt. Also remember that you need a coldplate which contacts the entire hotside of the pelt, and then you need to figure out how you are going to hang this huge apparatus off of your vid card without breaking it. (I've seen this done, but its rarely elegant)
The coldplate should be about 1/2" thick I believe since you will be air cooling.
Also, keep in mind the stress this will place on your PSU. Pelts draw a pretty considerable amperage, and you need to make sure your power supply is up to the task as you don't want to exceed its amperage rating as that could cause some premature PSU death. The rating can usually be found on a sticker right on the PSU.
I can help you with how to set it up and what to use, but nobody can really say for sure what temps or overclock you would get... That depends on the cooler used, the fan used, the quality of your particular GPU, and the method of temp monitoring. There are other factors also, so the bottom line is that is impossible to estimate with any worthwhile amount of accuracy...
But like I said, I would love to help you give it a shot if you want to try it. Fire off your questions.