Yeah, I'm going to call around.
The two sets of Terra Grapplers on it are 112S rated, so 112MPH. Been running those for about 100k miles though and that speed rating seems to work. 112S is the minimum I will go. I'd also run H or T.
For anyone curious about why Nitto is keeping the originals and the G2 Terras around, I called them today. They have no intentions of adding more sizes to the G2 line, so if a size is currently only made in the original generation, it will remain in production. So that puts them back in the running...but $208 a tire. OUCH.