They sell the 11W/mK and the 17W/mK pads. I use the 11s cuz they're cheap, but if you need the absolute best, go with the 17s. There is literally nothing better for sale, anywhere.
What thickness would you recommend?
*looks at pants* Well that's sort of personal question...

It depends on the thickness of the original pad, but you want to go as thin as you can. I used 1mm for the RAM chips, and 0.5 for the VRMs.