I forgot all about this thread.
Anyway, Gouki's durability is at the least in the mountain range. When fighting Gouken, they both leveled mountains while fighting with barrages of Hadoukens. Also, we has to consider powerscaling. Shin Bison, who is around Shin Gouki's power level (Prolly, may be lower, dunno), was able to survive a massive explosion that destroyed his base, mushroom cloud and all, which was done with nukez courtesy of Charlie. Also, he could stand without any discomfort in a deep sea trench. Which means his body is immensely durable all over, even t3h eyeballs. Oh, and he fought Gouken inside a volcano. Yey. Also, with a single leap while destroying the sunken ship with a kick, in that few seconds he went from the sea trench to above the surface. While doing a kick. Yey.