No but revving to 9,000rpm+ could cause bearing issues or at least more heat the diff/seals may not be able to handle. Plus you have the extra torque also creating more heat, and I do plan on tracking the car, so the diff will get a bit of a flogging (rotaries are meant to be hard on gearboxes and diffs).

3.757 (standard 1st with 4 speed) x 6,500rpm = 24,420rpm (aprox max input speed using a10 and 4 speed)
3.67 (rx7 gearbox) x 9,000rpm = 33,030rpm (35% increase in speed)
3.815 (rx8 gearbox) x 9,000rpm = 34,335rpm (40% increase in speed)

I have a feeling that the friction (ie heat) isn't directly proportional to rpm, but a square of it. I wish I remembered more from uni...

I'd rather get the lightest available that will handle the torque (ie H145), but I don't want to be changing it every few months due to bearing failures, etc.

Also is a LSD still available for a H145? If so where (quick google search wasn't helpful)