Actually there is some factual data on what the 7AT in the 370Z was designed for, which I found with some internet sleuthing in this thread over here:
Nood questions needing your expertise (supercharger on a A/T)
The bottom line is our 7AT (Nissan model number RE7R01A) is actually a Jatco model number JR710E transmission and is officially rated to handle 295 ft-lbs (presumably that's measured at the engine output, before drivetrain losses for rwhp). There's another version of our 7AT transmission that's used in FX50/QX56, which is rated for 443 ft-lbs (Jatco model number JR711E). IMHO, it seems like it would be worth pursuing the idea of swapping in a JR711E from a wrecked FX50/QX56 as a cheaper alternative to doing massive internals upgrades on our weaker model. I'm not sure if they're 100% compatible in dimensions and ECU hookups, etc, though, and at higher levels of forced induction even that one would need more upgrades.