I'm absolutely new to the idea of firmwares and stuff along those lines, however:
Looking on Wikipedia for "Tomato (firmware)" you'll see the only 2 mods listed with IPv6 support are
TomatoUSB and Tomato RAF.
The problem is both of them only have IPv6 in their Ext builds, which are not suitable for <4MB routers like my WRT160N V3.
Is there a way to enable the IPv6 option in a Std build? How would I do it or compile my own with IPv6 support?