The 650 HP is actually a low reading from the engine dyno (we had one peak of 675 HP) but it had a FLAT torque curve. This is the Recipe car and pretty tame combo. This was also using 104 octane unleaded gasoline.
I've owned the GN since I ordered it from the factory in '86 and it's been tweaked and played with over the years.
Tranny has been through several iterations and incorporates my own "blend" of Mike Kurtz's parts (the extra steels and shims and the hardened shafts and so on) and some bits and pieces from various learnings over the years.
According to the calculators, it should be somewhere in the 530-550 HP at the wheels at race weight to be in the high tens with my sixty foots (1.5x avg).
Thanks for the reminder ... have to update my "toys" list
Just bought some this weekend!