Actually as MakingMusic pointed out, development of GT5 didn't start at 2004. The first tech demo of a next gen GT was released in 2005 with the Vision Gran Turismo Trailer in E305.
Afterwards PD focused exclusively on GT5:P, and it was not until they released GT5:P Spec II, in April 2008, that they shifted the focus on developing GT5 full fledged.
I've posted this same things over and over again everytime a GT5 thread arises, so I won't even bother putting up the links, people wanting to check them out, search them at IGN, they're easy to find.
Current PC Build
CPU - i7 8700K 3.7 GHz (4.7 GHz turbo) 6 cores OC'd to 5.2 GHz with Watercooling (Hydro Series H110i) | MB - Gigabyte Z370 HD3P ATX | Gigabyte GTX 1080ti Gaming OC BLACK 11G (1657 MHz Boost Core / 11010 MHz Memory) | RAM - Corsair DIMM 32GB DDR4, 2400 MHz | PSU - Corsair CX650M (80+ Bronze) 650W | Audio - Asus Essence STX II 7.1 | Monitor - Samsung U28E590D 4K UHD, Freesync, 1 ms, 60 Hz, 28"
