A newly leaked GPU-Z screenshot of what is claimed to be the GTX 760 shows it may in fact be a new chip based on the GK104:
According to leaks that surfaced on ChipHell, NVIDIA is configuring a GK104 GPU with just three out of four GPC (graphics processing clusters) enabled, while keeping the memory and raster operations untouched. This approach would give the chip 1,152 CUDA cores, 96 TMUs, 32 ROPs, and a 256-bit wide GDDR5 memory interface. The card in the GPU-Z screenshot features 1072 MHz core, 1111 MHz GPU Boost, and 7.00 GHz memory.