What Graphics card is 12.5" long

It's not really a joke, actually; he's got a point. Most graphics cards top out at 11 inches.
You'll see generally dual-GPU cards have that kind of length; so they could accommodate a large cooler.
The Radeon HD7990 for instance.

Also, look at this 590:
http://www.techpowerup.com/gpudb/b679/asus-rog-mars-ii.html
It's got 365W of power to dissipate on two 520 mm squared GPU dice.
It has a cooler that occupies 3 slots and is 13 inches long.
 


Impressive, but the 690 is 12.1(vs 12) and the ROG 590 beats it ;)

On an off note: the card had specs that dwarfed even the 690(source: hwcompare) theoretically; but it ran so hot it just couldn't handle the specs and had performance much worse in practice.
 

I can only assume you have never seen this article?

http://www.legionhardware.com/articles_pages/ati_radeon_hd_5970_overclocking_problems,1.html

Something to consider is the fact that the Radeon HD 5970 is said by AMD to use 294 watts of power when operating at its default specifications. The PCI Express bus specification states that no graphics card should exceed 300 watts, and this is why AMD has been apprehensive about the clocking of the Radeon HD 5970.