GeForce 9800M GTS 55nm vs. 65nm overclocking

I read that the 512MB 9800M has a 65nm core, but to keep the 1024MB 9800M's TDP at 75W, Nvidia reduced the core to 55nm, because apparently the memory produces a good amount of heat. This has gotta make a difference for overclocking. I would assume that if heat were an issue, the 55nm one could have the core and shaders overclocked more than the 65nm one, but the 65nm one could have the memory overclocked more. As for me, I'm not worried about the core temp at all with my laptop cooler, but I am using the stock 120W psu, so should I just overclock the core and shader lightly but not the memory? (I have the 55nm one.)

Also I am wondering, I have 9c.20 bios, and the graphics card fan doesn't turn on until the GPU hits 82C, so if the GPU is hovering around 70C in an older game, no fan going, is it possible that other components like the memory could be getting too hot?